It's the context - the sniper thinks they're going to a dangerous hostage situation with somebody who has already killed some people, they're trying to stop someone who is killing people and threatening to kill people.

The caller is intentionally putting an innocent person in a lethal situation basically because the caller is an ass and thinks they're not responsible for what happens afterwards.

I'm not arguing about whether or not excessive force was used or if the police response was wrong in addition to being tragic (very well could have been) since that requires knowing a lot more about the case.

I'm arguing that a lot less nuance is needed to say the caller is responsible. I'd argue they intended to cause harm for bad reasons - maybe not death, but that would have been a known possible outcome.