ST. LOUIS • The FBI is investigating a claim that a St. Louis police officer killed an unarmed man as he begged for his life in the second of two violent confrontations Dec. 20.

A civil suit making the same accusation is expected to be filed Monday on behalf of the dead man's infant daughter.

The incident has separately spawned an investigation into a patrol car camera video that reportedly shows the officer with what appears to be an AK-47-style weapon in the first confrontation. Policy limits officers to using department-issued weapons, and that type is not included. It was not used for the killing.

A police spokeswoman said it was the department that asked the FBI to examine the killing of Anthony Lamar Smith, 24. The FBI confirmed the review, as did U.S. Attorney Richard Callahan.

"I think it's premature for anyone to reach any conclusion," Callahan said Friday.

Al Watkins, a lawyer representing Smith's 1-year-old daughter, said he plans to file a lawsuit Monday in U.S. District Court that will claim officers fired unnecessarily and planted a weapon with him.

The officer has been with the department for four years and has worked in the 3rd and 6th districts. He currently is assigned to communications.