If he latches on again, and doesn't let go, cold/tap temp water is a good remedy. You could hurt him more than he's hurting anyone else trying to pry him off.
If you've had him 2 years and this is the first bite, I would think you are in pretty good shape!
I hope the guy who was holding him wasn't, or isn't now, afraid of snakes! I let ambivalent people hold my BP and they usually end up liking snakes after. Shayna is a sweetheart.
Best of luck and keep enjoying him!