Regarding the timeline, it seems possible PM was lured to meet someone and went willingly/intentionally. He could have told MM he needed to be home at a certain time, or that he was going there without saying why, or maybe she was just aware that he was on the property but not in the house. If he arrived and things unraveled quickly, he may have called out or texted MM, who ran to help. I think it's possible MM texted AM that something seemed wrong, or that she was worried and going out to check. Then, when communication stopped, AM got home as quickly as possible. All conjecture, of course, but for me, the short timeframe doesn't, by itself, refute AM's alibi.