The real biggest error
At the end of the movie John clearly gave her CPR on the wrong side of her chest. The way she was laying and the way he was, he should have given her CPR to the side closest to him, but instead he did it on the other side... my guess is so Patrick could sneak up from behind and make it look like he was giving her CPR as hard as he could or something. Maybe it was just a weird angle, but there was one shot that clearly showed this.
Maybe I am wrong, but watch it again.
Also, how does holding up a bullet proof vest protect you from a machine gun or automatic or whatever the dude was shooting at him? lol
Other than that, I felt it was a better movie than I thought it would be.