Mahong left the homicide team, but David White is still there. He was previously in the Anti-Terrorism Team, but later, due to Jimmy and Mahong being seconded one after another, Hughes brought him over from the Anti-Terrorism Team to temporarily handle cases in the homicide team. After that, he stayed, but Jimmy was transferred to fieldwork, so the two of them actually didn't work together for long.
Now that Jimmy is about to take over this explosion case, David White will naturally follow Jimmy to handle it together. He must have already been informed in advance about his future assignments, so he didn't feel any resistance to Jimmy asking him to go out for investigation together, simply showing a sense of holding his duty before leaving.
Jimmy and David arrived outside the bakery where the explosion occurred, and it was still cordoned off, police lines taped around, with the doors and windows sealed to prevent anyone from tampering with the scene inside.
