I’ve watched it twice, and I’m still not sure. On first viewing, I thought Gordon killed everyone, but after seeing it a second time, I think Phil killed Hank, and then Gordon offed the rest of them. I also haven’t figured out a precise timeline, although my family assures me that Gordon did kill his family just prior to the new job.
I’m such a movie doofus. Someone help me out here…
Gordon killed everyone. First he killed his wife, baby and dog, then went to work on the new site and killed everyone else. I thought the last ten minutes of the movie made it clear, but then again the perfectly clear ending to Pitch Black had to be explained to me because I totally misunderstood it 
My memory is fuzzy on this, but Hank was the one who found the cache of coins behind the crematorium, right? When he went back later that night, he found an empty jar of peanut butter down in the cellar just before getting whacked.
I don’t know if the spoiler is necessary after the previous two posts, but:
Later in one of Gordon’s flashbacks, you see him loading a bag of groceries into his truck. Sticking out of the top of the bag is the same jar of peanut butter, indicating that he was the one creeping around the hospital at night.
Yup, Hank was the coin-finding guy.
I came up with my Phil-as-Hank-killer after the second viewing…first, because Phil reported to the group that Hank had told Hank’s woman/Phil’s ex that he was off to be a casino dealer (making me suspect that he KNEW Hank wouldn’t be coming back); second, because Phil flipped a coin that appeared to be from the stash that Hank had discovered.
Of course, I can also figure out why and how Gordo did it, too…
I wondered about Phil as well. Started a thread on it, too, but it died with only one response.
http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=170326
Man, that flick was good. Quite a pleasant surprise.
In another thread (which the board is too slow to search for at the moment), someone else speculated about Phil and why he had lied and told the group that Hank had said he was off to be a casino dealer. My response was, what makes you think he lied? Hank DID tell his girlfriend he was off to be a casino dealer; he found all these old coins, he decided to take them and abandon his current life for a new one, and he gave his girlfriend the brush-off. See ya later, sister. It’s not like Hank was a kind, giving character prone to sharing his good fortune with anyone, including his girlfriend. Besides, he probably thought he’d get a better girlfriend once he started flashing his cash around.
OOoh. Good point, Max. I hadn’t thought of that.
Darn. Now I’m really confused. Nothing new, of course. 