What else can they do? They can muster every last bit of sensibility they have and bring him down with non-lethal means. Multiple officers have him pinned to the ground - they've got the upper hand, and if they wanted to bring him in alive, they could have. Zap him again, or give him one good blow to the head to knock him out, or fuck it - shoot him in the leg!
They've got his weapon, he's in a compromised position, and they're armed and armored like god-damn combat soldiers. Buck up and take this guy in alive. You don't get to tell me how much of a dangerous job you have if you've got carte blanche to empty a clip into anything that threatens you.