No that isn't true and is complete nonsense, cops don't high five each other and congratulate one another on taking a life, no matter how much that person might have been seen to deserve it.
Mostly because in the head of the moment it can never be known what all the factors that went into a situation. Cops sure might congratulate one another for putting dangerous situation to an end without any other casualties or brothers in arms.
But this guy was an idiot, and I guarantee when cops end up being reported shot or killed, that will certainly influence the amount of compassion displayed towards them by others too.
I understand they have to take human life, I don't think it's ever ok to be proud you killed someone.