CHICAGO (CBS)–Surveillance video released by the Aurora Police Department Wednesday afternoon shows shooter Gary Martin as he prepares to ambush officers as they approach the Henry Pratt building in response to calls of shots being fired on February 15.

Five employees of the company were fatally shot that day, including human resources manager Clayton Parks, 32 of Elgin, human resources intern and Northern Illinois University student Trevor Wehner, 21, of Dekalb; hold operator Russell Beyer, 47, of Yorkville; stock room attendant and fork lift operator Vicente Juarez, 54, of Oswego; and plant manager Josh Pinkard, 37, of Oswego.

The approximately 8-and-a-half minute-long surveillance video released by police on Facebook Wednesday shows Martin as he prepares to ambush approaching officers. In the video, which is split into four screens, officers can be seen as they approach and enter the Henry Pratt facility, while Martin is seen on one of the screens showing the foyer of the interior. Armed with a firearm, he moves back and forth throughout the area, appearing to pace.

The only video of the interior of the building was shot in the foyer area, and the video has no sound.

Martin, who was killed in the shooting, was found in possession of a gun and eight pistol magazines.

Police said he fired 64 rounds the day of the shooting.

Portions of the surveillance footage taken from the day of the shooting were excluded to protect the privacy of the victims, police said.