Continuity mistake: Eric sits down after finds out who is in the game with Daniel. When he does, the walkie-talkie on the desk simply disappears between different shots. (00:56:40)
Continuity mistake: In the office when Detective Matthews and Kerry are arguing, Matthews' gun keeps changing position on the desk with no-one touching it. (00:09:10)
Continuity mistake: At the end when Det Mathews is in the same room as Saw 1, you can see the mirrors on the wall. Both are intact, when one of them was broken by Daniel in the first movie.
Continuity mistake: After Xavier's had his throat cut, he grabs Daniel's shirt and his hand is completely covered in blood. The camera cuts away and then cuts back, and suddenly his hand is bone dry. (01:15:30)
Answer: It was Zep, but he died because Adam smashed his head with a toilet seat cover.