He may have an accomplice helping to hide him. He had ample time to write up and send his threats, before doing his crimes and going into hiding. Nothing helps like having someone else getting you supplies while you stay hunkered down somewhere. There are groups of people in Oakland and Berkeley who would shelter him, but he could have a friend helping. Problem with groups is that they're watched by FBI. Problem with friends is, the FBI would be checking all his contacts. More likely he is on his own.