A water fight that eneded up with someone in the pool?
It's not like it just happened on its own. The police probably wouldn't do anything as my experience of them has been pretty crap, but it's still not good.
Even if (forbid) the child had passed away from this incident it would have been a tragic accident, but not a crime.
It very clearly would/could be seen as a crime. Accidentally killing someone can be ruled as manslaughter.
As OP said her other child would have reacted differently.
Yes, but her partner knows her son has mental health problems/anxiety. It's not like he doesn't know him. He most likely knew how the child would probably respond, at least to the extent that he would know the child wouldn't like it.
He did not have a full blown attack, it was managed by his inhaler
It was eventually resolved by an inhaler. An asthma attack that needs an inhaler but doesn't result in a hospital admission is still an attack. They are unpleasant and dangerous and can be fatal. Most attacks don't result in hospital admissions, but they're still full blown attacks.
Being a dickhead is not a crime!
It's not often a crime- it's still not good though. Most dickheads know the law and they will verge on breaking it with their dickhead-dom sometimes, but they will deliberately make sure they stop short of a cut and dried crime, so as to avoid prosecution. And of course they often use the excuse of 'it was just a joke.'