Plus there's the obvious angle. Accidents are part of life and are random. With any crime there's always the possibility of repeat, or worse, escalation (this w

Plus there's the obvious angle. Accidents are part of life and are random. With any crime there's always the possibility of repeat, or worse, escalation (this was an act of islamic terror, so chance of escalation if this goes unpunished is probably very real). A society must ensure that crime doesn't pay (because the reason crime is committed in the first place is obviously because it does pay, not necessarily in money, but it does pay). Arrest and punishment is essential for that purpose.