Hmm, unknown origin, unknown manufacture.
Heavily illegal…. Yeah, that’s something I want to keep around when I have kids.

Heck what fuze was in it?
Dirty trick for years has been to swap the fuze on a standard model for one out of a smoke grenade (no delay). You leave it behind for the bad guys to use, when they pull the pin and let the safety arm go, fully expecting 5 seconds before boom, it goes off in their hand.

The gent obviously didn’t have enough experience with them to make an informed decision, he did what was right based on the facts as he knew them.