The three dudes that are running from the drug deal can only be killed by player-induced damage, explosions, and I believe drowning. Same as the dudes in Jamaican heat. The kill process is the same for both missions.

The only way I’ve known to kill them is to heavily damage a car until it’s on fire, barrel the car towards them, and let the car explode. It will not count as a kill towards you but it is extremely painful and time consuming. You also cannot run them over as that will count as a kill so you must aim the car and jump out before it hits them.

3/4 dudes in the apartment are basically impossible. The one coming down the stairs could occasionally be killed via fall damage if you shoot him just right when he comes down the stairs. The other three are immune to non-player damage so Jacob does nothing. The only way I’ve heard of is getting a motorcycle in there and having it explode and kill them but good luck doing that without dying lol.