People Trapped in Haunted Church

by Lonnie Mason
(Springfield, Illinois, USA)

A hazy memory of a 70's or early 80's movie from my childhood stands out but I can't recall the name.

A group of people are trapped in what I'm pretty sure is a haunted church. The only two scenes I can still recall are:

1. A guy is using an electric saw to cut through a door. A girl goes to him, looks down over his shoulder, and he's actually cutting through his own arm.

2. A man manages to escape only to fall into what I guess is quicksand or a marsh. He gets sucked down and the movie ends.

Any ideas what this could be? Thanks!