Quick question! Help!

Hi guys, I just finished watching this for the first time. Like a lot of other people, I had questions about the ending. If he HAD transformed, wouldn't it be too late to shoot him and kill Satan??? That doesn't make sense to me. Was that a smile from him!?!? It seemed like it, but....

Also, someone else on here commented this:

Yeah OK, it didn't go for the cliched "Everything works out just fine & everyone's happy" ending, or the usual cheap "comes back from the dead" scare tactic, but surely they could have thought up another, more riviting way to end the film?? I mean Elias Koteas' character might as well of succeeded first time around, if they were going to end it like that...



So I don't know what this poster means by the "Elias Koteas' character might as well of succeeded first time around, if they were going to end it like that... " comment. Wasn't that character just the psychic? What would he be succeeding in? Wasn't that his only scene or am I confusing characters?!!!? Thanks in advance!!!!!!!