Let's look at AJ, he stands to gain all of her followers and extra $. He had a reason to leave early and be on the road. He had a car of the same color mentioned previously by police. Not only that, he had a class up the street that started at 5 on the same day. If he went ahead of time and set everything up for that class, then came back at 3:50, he would still have time to roam the halls, break some windows, murder MB and get back to start his class at 5. He would have the disguise in a bag (many of the items that were worn are shown on FB)
That being said, I can't picture him as the murderer. He appears to be easy going & motivating on FB. Nice smile...I don't know.
Courtney Tucker has 4 kids. If she were to be the perp, she would have to leave them for an unknown period of time alone. If she brought her phone, it would be in case the kids called and the reason she would be caught. That being said, I can't see the level of fury coming from her or any woman. I may be a bit naive but it was viciously brutal.