Wild thought, and maybe already discussed, but...could the perp have been damaging the church before Missy arrived just so they, appearing to be a POLICE officer, seemed to have a legit reason for being at the location?
As in, wait for Missy to walk in, confront her with, "Excuse me mam, we're investigating a break in here. I'll need you to come into this room here so as not to disturb evidence. Right this way..." Missy would likely be stunned and easily follow them into an area where she could be attacked. In this scenario the perp wouldn't even know they were on camera, until perhaps it occurred to them when maybe Missy said, "Did you check the video from the security cameras?"
It would also explain their lackadaisical meandering and light-handed blows to the wall. They just needed for her to see damage and be caught off guard. IDK. MOO.