1. One would argue he did what he was trained to do through  a murder simulator. 

Or it is only a game and it will not effect him negatively but  teach him hand-eye coordination. This game may not have triggered him stealing car but another force within him.

2.This case is not likely to happen again. This game has been out for years and no one playing the game has reacted so extreme due to this game.

"The video game industry gave him a cranial menu that popped up in the blink of an eye, in that police station," says Thompson. "And that menu offered him the split-second decision to kill the officers, shoot them in the head, flee in a police car, just as the game itself trained them to do."

3. Before having violent video games sold to minors, one should make  sure the minor is emotionally and psycological stable and should maybe have parental consent before purchasing the game.

4.Video game designers do play a role in violent crime, because with video games such as GTA a player is trained to kill a person without consequences like it would be the same in reality.

"the teenage brain is different from the adult brain. The impulse control center of the brain, the part of the brain that enables us to think ahead, consider consequences, manage urges -- that's the part of the brain right behind our forehead called the prefrontal cortex"