england-and-wales

First your ask:

But what about other people? About 400 people were injured as a result of the panic that ensued -- a reasonable person can anticipate this, so it seems like there could be charges for recklessness. Would it be a count for each injured person?

A defendant can be liable for panic-induced injuries to bystanders if those injuries result from a reasonably foreseeable escape attempt triggered by the defendant’s conduct. For example:

In R v Roberts, the victim jumped out of a moving car following unwanted sexual advances. The defendant was held liable for assault occasioning actual bodily harm despite the direct harm being caused by the victim's actions.

Therefore, if people are trampled or hurt while fleeing, and that panic was a natural and foreseeable reaction to indiscriminate gunfire, the shooter could, in principle, face one count per injured person, assuming sufficient causal connection.

This won't apply in every case. Lord Justice Stephenson (in the judgement of the aforementioned case) stated that if the victim’s act was sufficiently unreasonable, then it would be considered to be an independent voluntary act. Therefore, each case would require individual analysis.

Ultimately, in the same way that property damage is probably not worth considering in a case like this, the same principle likely applies here. There are far easier and more severe charges that can be established.

You also ask:

On top of criminal charges, could there also be a lawsuit for pain and suffering by the attendees (maybe a class action to simplify the proceedings)?

Each injured person has a separate course of action and these will not be aggregated automatically (although they can be). Given the indirect nature of the injuries in question, we look to the principles governing the tort of negligence. This requires us to establish that the defendant breached a legal duty of care, which caused the ensuing harm.

Again, on a case-by-case basis, this would require looking into the foreseeability of the harm and whether the shooter legally caused the harm to that individual (legal causation is not the same as factual causation). An individual who was trampled in the panic, would likely have a strong case. On the other hand, if several people were run over by a driver trying to escape by driving through the crowd, they would have a weaker case against the shooter and may want to consider proceedings against the driver instead.

Finally, you ask in a comment:

What about the emotional suffering that affects nearly everyone in the crowd?

This concerns the issue of pure psychiatric harm. In general, all claims for psychiatric harm must be a medically recognised psychiatric illness or a shock-induced physical condition.

The above requirements are necessary, but are not sufficient. After this, the law on negligence makes an important distinction between primary and secondary victims. A primary victim is someone in the actual area of danger; or who reasonably believed that they were in danger. A secondary victim is someone who experiences emotional suffering after witnessing injury to someone else; or fearing for the safety of another person (eg a family member).

The requirements for a duty of care to be owed to a primary victim are that there must have also been a foreseeable risk of physical injury which never manifested. However, the risk of psychiatric harm does not need to have been foreseeable.

On the other hand, the law is much harsher on secondary victims. They must satisfy the control mechanisms under the Alcock test (Alcock v Chief Constable of South Yorkshire Police). This requires the claimant to establish:

1. Foreseeability of psychiatric harm for a person of normal fortitude in the claimant’s position
2. The claimant must have a close relationship of love and affection with the person who is endangered
3. The claimant must be present at the accident or its immediate aftermath.
4. The claimant must see or hear the accident, or its immediate aftermath, with their own senses.

If all four requirements are met, the secondary victim will also have a course of action. These requirements are not always straightforward to establish, and there is a lot of case law addressing each of these requirements in more depth.

In another comment, it was mentioned that we could also consider"

the specific offence of possession of a firearm with intent to endanger life

That is certainly true. While this is more straightforward than the issues the OP referred to in the question (ie on the foreseeability of indirect harm and the possibility of damage for pure psychiatric harm), a complete answer should also mention this.

This statutory offence can be found in s16 of the Firearms Act 1968, and reads:

It is an offence for a person to have in his possession any firearm or ammunition with intent by means thereof to endanger life ... whether any injury ... has been caused or not

The application of this to the facts is straightforward. The offender clearly has the actus reus of being in possession of a firearm or ammunition (satisfying both). Similarly, they also have the mens rea by the fact that they clearly intended to endanger life. In fact, they would still incur liability under s16 if they had not killed or injured anybody.

france

Criminal liability does not care much about "lesser victims"

US and French penal sentencing differs significantly on three aspects:

• concurrence of jail terms
• standardization of sentencing guidelines
• plea deals

The differences are detailed below. Because of those differences, deciding to charge (or not charge) attempted manslaughter/murder in French courts is mostly about having a "fallback" in case the more serious charges are beaten (which would be difficult under the given fact pattern), and will not significantly move the sentence.

French jail terms are concurrent

Article 132-3 of the penal code:

Lorsque, à l'occasion d'une même procédure, la personne poursuivie est reconnue coupable de plusieurs infractions en concours, chacune des peines encourues peut être prononcée. Toutefois, lorsque plusieurs peines de même nature sont encourues, il ne peut être prononcé qu'une seule peine de cette nature dans la limite du maximum légal le plus élevé.

When, within a given procedure, the prosecuted person is found guilty of multiple related infractions, every possible penalty may be imposed. However, when multiple penalties of the same nature (*) are possible, only the highest possible penalty may be imposed.

In US parlance: every period of jail time imposed within the same trial is run concurrently.

Therefore, if you are found guilty of murder, the maximum sentence does not depend on attempted manslaughter attempts in the same series of facts. The actual sentence will depend on it, but it does not require charging the manslaughter attempts.

(*) Penalties are mostly jail time and fines, but specific infractions give rise to a fairly diversified set of "peines complémentaires": license revokation for drunk driving, ineligibility for corruption by public figures, etc.

Standardization of sentences

Furthermore, the US sentencing culture is heavily influenced by the federal sentencing guidelines. They might be non-binding on state courts, and can be deviated from in federal courts, but they still tend to encourage a "mathematical" view of sentencing (if guilty, then go through criteria A to Z, calculate a "score" and sentence accordingly). This has advantages (in particular, the USSG reduced a previously enormous race bias) but it also reduces the personalization of sentences (which is necessary for other reasons).

In French courts, there is no such standardization. Common infractions will often have a "tag price", but those "tag prices" might differ across courts, and can be "haggled with" considerably more than in the US. Mass murder is not a common infraction and will be sentenced with considerable individualization.

"Plea deals" do not exist for felonies

Given the above factors, a French prosecutor has much less control over the sentence than her US counterpart.

There was a considerable shift towards plea-deal-type procedures in French criminal law in the last ~20 years. I am not familiar with the various procedures but a key point of all of them is that (A) the prosecutor still charges for the largest offense, (B) the judge can reject the deal with much more discretion than they would have in the US.

This shift was mostly oriented towards mass infractions, where the "tag price" was already established due to a large market of sellers (offenders) and buyers (law enforcement catching them). Typically, those would be small-time drug dealing, petty thievery, and driving offenses. The policy goal was (obviously) to reduce the costs associated with the justice system.

Felony cases are (thankfully) rare and involve considerable risk for the defendant. Plea-deal procedures do not apply to them.

Civil liability and procedure

Civil liability

On top of criminal charges, could there also be a lawsuit for pain and emotional suffering by the attendees

A very rough summary is that French law, both civil and criminal, quantifies "pain and emotional suffering" through the incapacité temporaire / totale de travail.

Basically, non-tangible harm is quantified by medical certificates establishing that the affected person could not "work" for a given duration. "Work" is somewhat misleading though; see the governmental guidelines for medical practitioners:

l’incapacité ne concerne pas le travail au sens habituel du mot, mais la durée de la gêne notable dans les activités quotidiennes et usuelles de la victime (...). La période pendant laquelle une personne est notablement gênée pour se livrer à certaines des activités précitées est une période d’incapacité (...)

the inability does not refer to work in a professional context, but to the duration of a non-trivial impediment for the victim to pursue its daily routine activities [eat, cook, buy groceries, etc.]. (...) The duration of significant impediment to such activities counts as incapacité temporaire de travail.

It is very likely that people in the crowd, even if not hit by bullets, would exhibit some trauma symptoms giving rise to temporary and/or durable "impediment to daily, routine activities". This might also be the case for close family members of those in attendance, etc.

Class action (almost) does not exist in France

(maybe a class action to simplify the proceedings)?

Technically, class actions are possible under French law since 2014. However, they are extremely rare (this 2024 source counts 32 procedures in total, 6 of which did not end in a dismissal). They are also restricted to consumer law violations; a terrorist attack would not do.

That being said, "standard" lawsuits that look a lot like class actions do exist. It is not uncommon for a large number of plaintiffs with similar claims to be represented by a single lawyer (or team of lawyers). If a court in such a case suspects that various groups of plaintiffs have diverging interests, or that individualized factor will matter, they will most likely remind the lawyer(s) of their obligation about conflicts of interests. This would be class certification in all but name.

Furthermore, (part of) the public policy behind class actions is to discourage bad behavior that causes small damage to numerous persons. French law has a different approach to that problem, by giving standing for certain moral persons to sue. Hence, environmental NGOs have standing to sue in administrative court to cancel building permits on undevelopped land, consumer groups have standing to sue in civil courts if a defective product was found on the market, etc. Such moral persons are entitled to damages even in the absence of individualized injuries, and they do not have to redistribute the proceeds to injured parties.

(I do not have the specific knowledge to comment on the exact economics of such cases, nor do I care much to investigate, given that this is not central to the question asked.)