He does that a few more times over the next few weeks, getting progressively closer to his targets each time. One time he does in fact go after a human, but the shock of having his first arm ripped off by Addy is enough to snap him out of it. Also, his power grows another arm pretty quickly, so, oops?

Eventually he feels confident enough to shift his skin and eyes into more natural colours and actually talks to a human. It's about as awful as he'd expected it would be, but he's getting used to the awfulness so he doesn't actually kill anyone!