The Metropolitan Police Department has ruled the death of 33-year-old graduate student Patrick David Casey a homicide resulting from “blunt force trauma.”

Though investigators have identified suspects, MPD is not releasing the tapes with footage of the Sept. 23 confrontation between Casey and three individuals to the public, officer Araz Alali said. He said Casey was declared brain dead Tuesday, but legally declared dead Thursday.

Casey and three individuals were arguing outside the McDonald’s restaurant at 916 M St., NW at about 2:40 a.m. Friday, when the verbal fight escalated and turned physical. One suspect punched Casey and he fell onto the pavement, incurring head trauma. His mother said GW Hospital tried for four days to keep him alive.

The D.C. Office of the Chief Medical Examiner conducted an autopsy Thursday.

Casey, an Afghanistan war veteran, came to the District in August to earn a master’s from the Elliott School of International Affairs. The Clifton Park, N.Y. native had an “infectious grin” and, despite his 6-foot-4-inch stature, was a “big teddy bear,” family and friends said.