Visible crew/equipment: When Mary and her neighbour start to walk back up towards Mary's house, in the shot from behind them, you can see the distinct shadow of the camera cast on their backs. (00:07:59)
Audio problem: In the scene where the polite leader is addressing the Sandins for the first time he takes his mask off and starts talking to the camera but he is muted until James unmutes him. If you watch the polite leader while he is muted he mouths the words "Mr. And Mrs. Sandin" before he is unmuted. However when he is unmuted we hear him finish that statement by saying "Mrs. Sandin" again. (00:33:25)
Continuity mistake: In the scene where Ethan Hawke is talking through the safety glass in the barricade to the polite leader of the gang outside, the leader shoots the loud-mouth guy standing to the right of him, using the pistol in his left hand across his chest. Immediately after that they show a top shot of him dropping his right hand holding the gun. (00:46:00)
Continuity mistake: Near the end of the movie as the family is about to be killed by the neighbors Dwayne comes in and shoots Mr Cali, then grabs Grace around the neck. You can plainly see her hands as they hold Dwayne's arm and they are empty, then just before he lets her go a knife suddenly appears in Grace's hand. The knife then vanishes when he lets her go. (01:14:55)
Continuity mistake: After Mary slams Grace's face into the table, the blood on her face keeps changing size and shape.
Continuity mistake: When the mother is pressing the letter opener to the homeless man's wound, the girl wakes up from being knocked out. She sees what her mother is doing, and begins to cry. A tear runs down her eye and across her nose. A little bit later, it shows her again. She has not moved at all, but now her face is dry with no sign of the previous tear or any others.
Other mistake: When the security system is armed, you can see the barricades are smooth steel panels running inside the outer walls, obviously on runners. Now, how do you attach a chain to a smooth steel panel and how do you rip it out without bringing the whole wall down? When Charlie lets the fugitive in, the panel is at least 1in thick. There is absolutely no way anyone is getting through that without specialised tools or heavy machinery.
Answer: These purgers are pretty crazy. They were hunting this person, a homeless man, and they wanted to kill him specifically. They wanted their prize, the trophy of their hunt. And they won't let anyone stop them as it's their right. So being blocked from their target only increases their desire.
lionhead