I've worked on some cases in the years since retirement, so I've learned a little as I went along. I only work on cases with video footage or a still shot that is relevant to the case. I've come to a few conclusions in this case, but I've only been here for a few days so forgive me if I say something stupid. I've deduced some things, one of which is related to the report that Prisma had a gun. This may not seem relative, but it is for a secondary reason.
I believe that it's true that Prisma was carrying a gun. Whether she pointed it at someone is not an issue in this for me, only if she had a gun. Two things I saw on the video convinced me. To begin with, she ran from her car to the building, something not necessary unless she was very late for something, or in this case, if she feared that the cops would show up. She knew they would be called and she knew she better drop the gun somewhere before they caught up with her. That explains why she drove to her ex's building and why she ran to the building from her car. She needed to drop the gun where she could retrieve it later and she needed to hurry before the cops showed up.
Next, when she entered the building she took a strange route. She circled to the right of a post, instead of walking straight ahead. I think she did that so that the post could block the camera's view, so that she could slip the gun into her bag without being recorded. If you watch closely you'll see her make a very quick transfer of an item from her hand into the bag, doing that mostly while hidden behind the post. The item was the right size and generally fit the description of a handgun, I saw it enough to be confident saying that it was a hand gun.
One thing I'm not sure of is, she was said to be talking on the phone with the baby sitter I believe, so did she already discover that her ex wasn't there and if so, how did she do that? If she didn't go upstairs yet and she's talking to the babysitter, how could she have known that he wasn't there? I would have expected her to leave that building if her ex wasn't there but she lingered for awhile and I wonder why? I'm not sure, maybe you guys know? There are 3 more things that we know and these things fit the theory that I'm working on. I'll talk about that later when I know more.
Just one more thing; I have a hunch that the clues needed to solve this aren't hidden well enough to count the old guy out. Give him a few days or a couple weeks, ......then we'll see.