Needed clarification on one teensy little thing..

*Major spoilers, you have been warned!*

I'm going to make a few observations/assumptions here first, please let me know if any of these are wrong:
1. In this movie, satan and his cult are not shown to wield any supernatural powers, other than the ushering in of the second-born (as satan-incarnate)
2. All supernatural powers, including the plagues and hell-fire, were produced by the 'good' side
3. As a corollary of point #2, Father Costigan was warned (at the beginning of the movie) by the 'good' side that Katherine's life was in imminent danger

So considering the points mentioned above, here's the question - when Father Costigan is warning Katherine about Loren being 'the evil one', why did his room catch on fire (quite possibly killing him in the process)?