Reach at least 60% friendship with Little Jacob, then call him up to buy some guns. After purchasing weapons, Little Jacob will drive away in his car. If Little Jacob gets stuck with his car, you can shoot him in the head. You cannot open the doors of his car and it will disappear if you get in another car. When you leave the area where you killed Jacob, he will then call you up to ask you if you will give him a ride back home from the hospital. He survived the headshot, apparently.