Guess what happened....

You stumbled yourself on a tiny rock, while you were running towards the Firefighter. Your trap turned fatal, you died. Meanwhile you fell, your gun went off from your hands, straight into the Firefighter's hands by accident. Police arrives, thinking the Firefighter is a killer.

The Chinese smuggled rifles into Liberty City again and he manged to find one, he was so impressed by the rifle that he held it in his hand as if it were his own. A bit later a cop saw him, seeing his firetruck had no water to fend off the cop, he decided to play with his wonderful new toy.

A North Korean spy satellite fell on you, and that's why there's a soviet made weapon there.

Looks like an AK to me.

AK is soviet. (:

Everything in North Korea is soviet made, original or modified.

Wow ur right... it looks like AK... but how can it be ak? there is no magazine... When ur reloading in GTA IV magazine is still there...

And that supports my theory of the satellite, the officer couldn't die of a shot since the AK is not loaded;)

Ok my theory is, that the fireman dropped the mag, it felt under the fire truck and the cop is trying to find it xD