I removed all my mods, and the scripts folder and everything, but i was having the same problem. Today around at 2:30 i was playing mcnr and it was so good but today at 13:30 it gone wrong, it was shooting 3 shoots again. That was the moment that i was thinking in reinstall gta3.img maybe that was the problem.
Edit: Plus yesterday i was having problems with tazer too 3 shoots, i have mods of texture skin and sound of weapons.