Following abrupt retirement announcement, William Gross says he has no plans to run for office Email to a Friend William Gross joined the Boston Police Department in 1983.Craig F. Walker/Globe Staff William Gross, who made history as Bostonâs first Black police commissioner, announced Thursday that heâd retire from his post a day later, ending a 2½-year run atop the nationâs oldest police department and departing amid a national movement demanding reforms and accountability in law enforcement. Gross, who was mulling a run for mayor, told the Globe Thursday afternoon that he had no plans to seek office following Mayor Martin J. Walshâs nomination as labor secretary in the Biden administration.