The injured deer was suffering, so the Arlington County police officer shot it in the head. When that didn't kill it, the deer was run over by a cruiser. Finally, a bag was placed over its head and it suffocated.

Now, an Arlington police officer is under internal investigation for his handling of the incident last month.

The sergeant, whose name was withheld by authorities, faces administrative sanctions for the methods he chose June 18 when trying to destroy the injured deer, said Matt Martin, a police spokesman. The officer is not on administrative leave, nor have his duties been redefined, but the department wants to examine its policy on injured animals.

"We recognize [the entire incident] showed poor decision making," Martin said yesterday. "If administrative sanctions are recommended, they will be implemented."

Martin said the officer was called to the 6900 block of Williamsburg Boulevard about 6:40 a.m. after the deer jumped over a guardrail on Interstate 66 and plunged 30 feet to the road below. After consulting with his supervisor -- a lieutenant in the patrol division -- the officer fired a single shot at the deer's head, Martin said, in accordance with the department's policy to kill any suffering or dangerous animal.

But the deer didn't die.

Instead of shooting the animal a second time, the sergeant authorized two other responding officers to drive a cruiser over the deer's neck. That, too, did not kill the animal.

Finally, Martin said, the three officers wrapped a plastic bag around the deer's head and suffocated it. A photograph of the dead deer and the sergeant was taken by one of the other officers, but Martin said the sergeant's explanation for the Polaroid was that it was needed for the incident report.

The department, Martin added, is conferring with other agencies on their policies so that Arlington County, which responds to one or two such incidents a year, is better equipped to handle the situation next time.

"This is not how our police department normally does business," Martin said. "This was an isolated incident, something our officers are called upon to do only a couple of times a year . . . but it's not the kind of judgment that we expect out of our supervisors."