Let me use RAT logic, here.
She moved away to Virginia to try to get away from this violence.( she must have known something was up regarding her son...(hit?))
She came back to Chicago (no reason given).
Her son gets murdered less than a few weeks back.
The mom caused her son to be murdered.
Yes good questions. Was her son falling in with a bad crowd, which prompted her to move away in the first place? Then they move back, he reconnects with the gangs, and he pays the price? I bet there’s more to this story.