CHICAGO (CBS) — Attorneys for an unarmed man who was shot and killed last year by an off-duty Chicago police officer have asked the U.S. Justice Department to investigate the shooting.

WBBM Newsradio’s John Cody reports attorney Jeffrey Granich narrated footage from a Chicago Housing Authority security camera inside the building at 1815 W. Monroe St., where Marlon Horton was shot and killed on Sept. 7, 2013, during a confrontation with a CHA security guard and an off-duty cop.

The video shows security guard Shaquila Moore and Police Officer Kenneth Walker pointing their guns at Horton just outside the building, after what appears to be a prolonged shouting match.

After a few minutes, Walker shot Horton in the chest, and Horton fell to the ground, bleeding.

Granich said both Walker and Moore called 911, but neither provided any emergency medical assistance to Horton as he bled to death, even though a dispatcher advised told them to try to stop the bleeding.

“’Put a dry towel from wherever he’s bleeding. Keep him calm.’ No one does anything,” Granich said, citing a transcript of the 911 calls.

Granich noted, at one point after the shooting, however, Moore bent down near Horton to pick up a cup of coffee she had set down earlier.

He also said Walker might have been sleep-deprived, and angry that Horton had urinated on a car outside the building, but he said there was no reason to shoot Horton, who was unarmed; or to then stand around and do nothing while he died of his wounds.

“My question is, if this were a woman, if this were a police officer, if this were a white college student, would they be allowed to lay there on the ground, and bleed to death, with six Chicago police officers standing there, in-scene, doing nothing at all,” he said.

Police Supt. Garry McCarthy said the officers fulfilled their duty by calling 911, and were traumatized by the shooting.

“The officers are going through trauma at that point, then most of them go for counseling after incidents like that,” McCarthy said.

Granich was skeptical.

“Clearly, Officer Moore was not so in shock that she still had the presence of mind to get to her coffee before it got cold while Marlon Horton grew cold and died,” he said.

The shooting remained under investigation by the Independent Police Review Authority.