1. Go to the part in the movie where Trevor is fighting with the two kids after he saves his friend from getting beaten up.
2. If you look carefully, when one of the kids stabs Tevor, the knife didn't even puncture Trevor's flesh! You can see it because after the kid takes the knife out of Trevor's body, it came from under his armpits, not the wound!
This is a pretty stupid slip-up. It's not like they are going to kill the poor boy just to make it look realistic. You have to give them a little credit for NOT stabbing him.