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.

His attorney, Neil Bruntrager, declined to comment Friday on whether his client was carrying an AK-47-style weapon. But the lawyer said that Watkins' allegations are "completely unsupported by all the known evidence."

Watkins said the claims are based in part on what the mother of Smith's child heard during a cellphone call she had with him during the incident. Additional elements include the video and an audio recording made by the OnStar motorist assist system, which turned on when Smith's car crashed during a pursuit.

Watkins said he has heard the OnStar recording, which he said catches the sound of moaning followed by gunshots. He said he has not seen the video.

Smith's pregnant girlfriend, Christina Wilson, 31, told the Post-Dispatch shortly after the shooting that she was on a cellphone call with Smith when he was shot.

"He was crying for help," she said. "I could hear him moaning, 'Oh, oh.'"

Police were put on high alert after Smith's shooting, as graffiti threatening officers was painted on a restaurant where the Smith case began.

Officials said at the time that Smith was confronted by police after being suspected of a drug transaction near a Church's Chicken restaurant at Thekla Avenue and Riverview Boulevard.

Authorities said that when officers first approached Smith's car, he reached for something and drove toward one of them, so the other fired. The car continued about a mile to West Florissant and Acme avenues, where there was a collision with a police SUV.

Officers said they again approached his vehicle, ordered him to show his hands and fired when he reached under the seat. Police said they found drugs and a gun in Smith's car.

Wilson, who was engaged to Smith, told a reporter in December that she didn't believe the gun found with him was his because "it was a revolver and these days everyone carries an automatic."

She also said he probably was reaching for a cellphone.

Watkins said Smith was a known car thief but not a drug dealer.

Court and prison records show that Smith was a suspected gang member who served prison time for theft, weapons and drug charges.

Smith was found with a .38-caliber revolver hidden behind his back in June 2006 after he and several others fled from police. He pleaded guilty and received probation. In 2009, he was caught running from a stolen car and sentenced to three years in prison.

In subsequent brushes with the law, Smith was caught with marijuana but claimed police planted it and got a confession by shocking him with a Taser.

In 2010, Smith pleaded guilty of selling a controlled substance and unlawful possession of a firearm. He admitted selling marijuana to support his family.

He was paroled from prison on May 23, declared an absconder four months later and was wanted on an arrest warrant when he died.

Jennifer Mann and Denise Hollinshed of the Post-Dispatch contributed to this report.