While I think I know the answer, I am compelled to ask, 'Did they know the suspect was a U.S. citizen before the attack?
In their 'zeal', the officers chose to violate what we in the U.S. consider proper, and(standard operating) procedure by failing to identify themselves before, and even during the assault.
I agree with Vox that the man is (very) lucky to be alive.
Such victims are frequently killed in the United States, and....
The police are not even charged...at all.