A gunfight erupted last night between an off-duty police officer and two robbers at a McDonald's restaurant in Southeast, killing one of the robbers and wounding a customer, District police said.

Shots were fired about 10 p.m. at the restaurant at 1539 Pennsylvania Ave. SE when two gunmen demanded money from a cashier, said Capt. William White III, a police spokesman. Both were armed with pistols, he said.

According to White, the shooting began when the officer, who had been working in uniform as a security guard on the restaurant's second floor, confronted the gunmen.

White said the robbers announced the holdup, and then one vaulted the counter and placed a gun against the neck of a female cashier. He was emptying the cash register when the officer, Michael Paul Clay, ordered the two gunmen to halt.

As shots were fired, White said, customers dived under tables and fled for doors. Moments later, he said, one of the robbers lay dead on the restaurant floor, a pistol beside him. The other robber fled, but White said witnesses could provide only a general description of him.

The wounded customer, a 32-year-old man whose name was withheld until relatives could be notified, was initially taken to Greater Southeast Community Hospital in guarded condition, hospital officials said. But the man's injuries, two gunshot wounds in the upper thigh, did not require surgery and his condition was upgraded to stable early this morning.

Clay, 39, a 17-year member of the force who serves as a patrol officer in the 1st District, has been placed on administrative leave with pay while the shooting is investigated, White said. The gunman's body was taken to the D.C. medical examiner's office for an autopsy.

White said it was unknown how many times the gunman was shot or where his body was struck. He said ballistics tests would determine who fired the shots that hit the customer.

It was unclear how many customers and employes were in the restaurant when the shooting began, but a witness who was approaching the restaurant when the robbery started said there appeared to be few people inside.