This is my first comment on this site. This is how I think it all played out, but is my opinion only:
I think it was a planned crime (robbery, carjacking and/or rape) but the victim was random. In one of IY’s prior robberies, he only got $40 from someone so there isn’t a huge wealth criteria to be his victim (this makes sense because Aniah wasn’t carrying a purse, drove a “normal” car and may not have appeared super wealthy).
Yazeed was possibly staying in a local hotel or w/ friends/other gang members. He either (a) walked to the Chevron OR (b) he and a friend drove the grey car. IY saw AB and decided she would be the victim and he forced her into her car at Chevron.
A witness saw the kidnapping. It was possibly the person in the grey car (assuming (a) above). They left the store before going inside. Cashier saw the grey car and AB’s car leave. He/she assumed IY was in the grey car b/c maybe he was the only other customer in the store at that time. This accounts for the first reports of IY leaving in a grey car. OR (if (b) above) the friend left in the grey car, and again, it was assumed that IY was driving. OR the witness was the cashier (LE said witness was outside to protect cashier’s identity) or it was just someone driving by/stopped at a light. Who it was really isn’t important, just trying to account for the mysterious grey car.
IY took AB to where he was staying or to a deserted location (friend possibly followed in grey car). During the drive, she fought, he hit something and it caused the car damage.
Snapchat messages – AB got a message from her roommate and AB told him she needed to text back or the roommate would call her parents. IY didn’t want to alert her friend so he let AB text her back. AB texted back with cryptic message about “Eric” knowing her roommate would not know that name and/or would think it is unusual. This would not alert IY to anything but could possibly alert suspicion in her roommate. Roommate said she was going to bed and AB knew her hint didn’t work. “I’m so, so sorry. I love you too” could actually be a message to her family (something that wouldn’t be too obvious for IY). Her phone was then turned off.
Within one hour, she was beaten, robbed and/or raped (possibly by more than IY) in Auburn. Perhaps, IY discovered her step-dad is a pro-fighter. Instead of leaving her alive (as in the other cases), he panicked and thought he needed to kill her so she couldn’t identify him. Or maybe her beating was so bad that it killed her unintentionally. Or maybe he killed her on purpose.
He put her in the passenger seat in her car and drove toward Montgomery (friend possibly followed in grey car). She was dumped in the forest on the way to Montgomery or in the Alabama River (I believe there was a former victim that never came forward who was threatened with being thrown in the AL River). He left her car at an apartment complex. A friend picked him up or he went with the friend in the grey car.