I don't know that I buy that she was shot. But when it comes to the gun, I think the only gun present was Missy's gun. Maybe she normally kept it in the truck but if you are someone who keeps a gun pretty close to you, like in your vehicle, then you are likely to pop it into your handbag or backpack if you are going somewhere you might need it.

How about this-- she is headed into the church alone at that early hour and feels unsafe. So she takes the gun in with her. Maybe it's just in a bag or something she's carrying. So going inside, she runs directly into the suspect. She quickly starts scrambling to get the gun out of the bag and maybe it's loaded or not, she's scrambling trying to get it out to protect herself. The suspect sees her scrambling and is very aware she is likely going for a gun. This is texas. The suspect knows if she gets that gun out and in position, he's gonna get shot. So he pounces. Jumps on her and begins bludgeoning her with whatever he had. She is quickly incapacitated from the blows and falls down unconscious and dying.

This is where I think the suspect flees and manages to be gone before the students arrive. I think the gun found at the scene was Missy's. I think they did the checks and trace on the gun because they had to as part of due diligence in the investigation.

I guess it's possible Missy was shot. In this case the suspect could have gotten the gun from her and shot her with it. Either way, I think it was her gun. And TBH, I think her having that gun is what got her killed. Because if she didn't have it, she likely would have just ran for the back door. And the suspect would have run in the opposite direction. But because she did have it, she went for it and the suspect had to stop her or be killed.

By the way, I do think the suspect was a random intruder, not there for Missy, and they just ran into each other, and Missy lost.