@BCTheEntityThere's really no way to know, that's the problem. Everything Donny does is iffy. Perhaps he could be weeded out of hiding by a dozen vigilantes methodically and carefully combing an area for traps in a tightening circle, but even then it's a big gamble.
Best advice I can give is don't be afraid to fight like scum. I'm talking "Jump out of the shadows with an Uzi and try to unload a clip point blank from behind" dirty. If Donny hadn't been distracted and blown his own cover when he first saw Red Claw (he was whistling and strolled out into the open), he'd have absolutely tried to kill Claw as quickly and as cheaply as possible.
The chance to kill Donny will come sooner or later.