Your friend got murdered and there are no suspects, but you know that he is involves with something illegal. Investigating it would be dangerous but it won't stop you from doing it. You are a sharp-shooter and you know a contact that can supply you a gun with no papers. Getting a gun with papers is not your option since you are going to use this to kill some criminals and you don't want it to be tallied to your name. The cops would easily know and they would take you down instead of the culprits who killed your friend. The justice system is not great in this country and won't certainly protect you. You need to take matters into your hand if you want something done.
The idea here is to drive in a certain area wherein you need to park your car. Carefully park it and from then on, you would need to kill some bad guys as they would come after you. Those guys would not stop on shooting, so it would be best to hide and shoot to take them out. You need to avoid their bullets since you are not bullet-proof. After that, you need to drive your car to the exit point to get out of that level.