Fujimotos We don't, as a rule, use lethal force. We don't shoot people unless they are presenting a genuine threat to life at that moment. Salvador was not doing that when he was being apprehended.
In America, they shoot people far more loosely, but they also allow the population to be armed with guns. The two are closely linked.
Had he posed a risk to life, someone would have had to make a horrid assessment on whether it was worth discharging a weapon near to children. Even the best shot can get it wrong, it could have horrendous consequences.
As it is, Salvador is unwell, and he should get treatment. When he's treated, the knowledge of what he has done will probably be enough punishment, but his freedom is also severely limited.
Your personal opinion of Broadmoor and similar institutions is of no real relevance, but they certainly don't breed their own type of insanity. That's ridiculous. Have you been inside one, or is your opinion based on third-hand knowledge? I've visited a few people inside similar places, and the staff are trained to help people integrate, and to turn people around. To treat those who the rest of us wouldn't want to be near.
Being institutionalised is always a risk when you take away someone's freedom and keep them in a prison-like environment, but that's necessary under these circumstances. It isn't insanity.