A Dallas police office is under criminal investigation after a surveillance video surfaced that indicated he may have lied on a police report about shooting a mentally ill man who he claimed had a knife.

Joyce Jackson said that she called the Dallas Police after getting in an argument with her son, 52-year-old Bobby Gerald Bennett, on Monday and the dispatcher promised to send specially trained officers.

Although Jackson had informed the dispatcher that her son had a knife, surveillance video provided by neighbor Maurice Bunch shows Bennett sitting in a swivel chair rolling away from officers in the middle of the cul-de-sac. With officers about 20 feet from him, Bennet stands with his arms to his side.

The officers raise their guns and about eight seconds later, Ofc. Cardan Spencer fires four times. Bennett is hit once in the abdomen.

An affidavit obtained by Dallas Morning News said that Bennett took "several steps toward them with the knife raised in an aggressive manner."

But Bunch said that the surveillance video tells a different story.

"When the officers told him freeze, he complied," Bunch explained. “He did not move an inch, in suspended animation; he just stood there, you know? Bobby was conscious, he knew exactly what he was doing because I had been talking to him prior.”

"It took them no time to start shooting," Bennett's mother pointed out. “When you’re with a mentally ill person, you don’t just start shooting. They had told me there would be someone special there to help him.”

Attorney Robert Rogers, who is representing Spencer, said that the officer's situation warranted using force.

"The facts and circumstances known to Officer Spencer at the time completely justify his actions," Rogers insisted. "Obviously there is much more to this situation than that video."

Spencer has been placed on administrative leave indefinitely pending the outcome of the investigation.

Bennett was charged with aggravated assault on a public servant. He was listed in serious condition at Baylor Medical Center.

Watch this video from WFAA, broadcast Oct. 17, 2013.