Continuity mistake: When Tommy is shot, Tuddy is holding his shirt, but in the very next shot, he isn't, and he's much further away from him.
Continuity mistake: After Tommy shoots and kills Spider, Henry sits back up and puts his hands down from covering his ears twice.
Continuity mistake: After Karen's been harassed by her neighbour, Henry drives her home and tells her to walk home. When Henry steps out, she's nowhere to be seen. She couldn't have walked all the way to the house in that short time. She couldn't have run, either, being as weary as she was.
Continuity mistake: When Karen is over Henry pointing the gun at him, the trigger is pulled all the way back. The gun also goes from blue steel to silver.