Others have also commented on this, but here are some thoughts on part of the timeline, based on posts in the handy "media reports/no discussion" thread.
http://www.websleuths.com/forums/sh...19-Lake-Forest-Jan-2018-Media-*NO-DISCUSSION*
Based on reports on that page, there seems to be more than one timeline, perhaps based on different versions told by the friend to the police; events tend to get later in more recently mentioned timelines. Earlier media reports quote various sources (BBs parents and an attorney friend of the family, but would have to double-check) say that BB texted friend/driver at 9:30pm, that he picked BB up at some point, and that they got to the park at 10:30pm. The friend claimed that at some point BB ran off, and at 11:30pm the puzzling text was sent. Shortly thereafter BBs borrowed phone was turned off.
In the affidavit, the friend says that after he picked up BB, they spent some time hanging around in the parking lot of Hobby Lobby and didnt get to the park until close to midnight. He then claimed that BB exited the vehicle and that the friend waited for him until around 1pm.
One crucial difference between these two timelines is that the first implies that while the puzzling 11:30pm text could have been sent by BB after exiting the vehicle, it also couldve been sent by the friend after he killed BB. The second timeline makes it sound more likely that BB sent the text himself before exiting the car and also that BB turned off his own borrowed phone.
One possible motivation for the discrepancy is that the friend may have realized that the police might figure out from his own cell phone records and those of BBs borrowed phone that he was with BB when the text was sent. He also may have been trying to fit his account to when he or his car might've appeared on surveillance video.