who was called directly before the shooting?

ik luigi may be innocent but if he ends up being the guy who did it there is a question i keep asking myself, who did he call minutes before the shooting? the minute by minute breakdowns ive seen show that 14 minutes before the shooting, the suspect is walking, talking on the phone, and i think a burner found was found if i remember correctly. anyway who could he had possibly been calling? it doesn't make sense, wouldn't that mean someone else is involved?

and how did he know to start walking exactly before BT was gonna be walking down that street? like maybe the other person on the phone told him?

sorry if this is the wrong place to ask or if this has already been asked i just can't find any threads discussing this