Aurora, Illinois shooter Gary Martin, 45, killed five co-workers during his murderous spree in February. Police have now released surveillance footage from the day

This is the terrifying moment the shooter who killed five co-workers in Aurora opens fire on police as officers desperately try to stop his murderous spree.

Surveillance footage from the February 15 mass shooting released Wednesday shows the moment Gary Martin, 45, prepares to ambush law enforcement officials after being told he was being fired from his job of 15 years.

The clip, posted online by police, shows four camera angles from Henry Pratt Co. in Aurora, Illinois, right after Martin pulled out his gun and began shooting at his industrial valve manufacturer workplace.

It shows the shooter, who had one pistol and eight pistol magazines, in the lobby area of the building, looking out of a window and pacing back and forth.

Officers are seen running towards the building as police cars swarm the parking lot and Martin, who is carrying a black ammunition bag and fired 64 rounds during the incident, picks up a bin of cleaning products, throwing them to the ground.

He then begins to shoot as police duck behind SWAT shields.

The clip, posted online by police, shows four camera angles from Henry Pratt Co. in Aurora, Illinois, right after Gary Martin began shooting at his industrial valve manufacturer workplace

It shows the shooter, who had one pistol and eight pistol magazines, in the lobby area of the building, looking out of a window and pacing back and forth before he opens fire

Later an armored police truck arrives and rams doors from where Martin is shooting. As officers approach the door the shooter continues firing rounds through the glass.

Seven armed officers can be seen entering the workplace and police are said to have searched the building for more than an hour before hunting down the gunman, shooting him six times and killing him.

An autopsy showed one of the wounds was likely self-inflicted to his jaw.

Later an armored police truck arrives and rams doors from where Martin is shooting. As officers approach the door the shooter continues firing rounds through the glass

Seven armed officers can be seen entering the workplace and police are said to have searched the building for more than an hour before hunting down the gunman and killing him

Police secure the area following the shooting at the Henry Pratt Company in Aurora, Illinois

Right after learning Friday that he was being fired from his job of 15 years at the Henry Pratt Co. in Aurora, Gary Martin pulled out a gun and began shooting

Posting the eight minute long clip online police said they were 'not careless in their judgement' but said the footage is a 'matter of public interest' and part of their 'ongoing commitment to transparency within our community'.

They said: 'We have chosen to publish a portion of the surveillance video which captured the horrible shooting event on February 15, 2019.

'As with our decision to release audio related to this event, we were not careless in our judgment here, and we understand the disturbing nature of these images.

HR Intern Trevor Wehner, 22, was killed on his first day on the job

'We understand, however, that as a matter of public interest and our ongoing commitment to transparency within our community, we agree that you have a right to see for yourself what transpired at the Henry Pratt facility that day where, sadly, five members of our community lost their lives, and five of our police officers were shot while simply doing their jobs.

'This video depicts the shooter as he prepares to ambush approaching officers, and shows the officers’ initial approach and subsequent entry into the Henry Pratt facility.

'The shooter was in possession of one pistol and eight pistol magazines, and we confirmed that he fired 64 rounds during this incident.'

The video, which police say has parts removed due to privacy, is split into four screens and has no sound.

It shows three views of the parking lot and one from inside the lobby. There is said to be no further surveillance video available from inside the building. The clip does not show Martin killing his colleagues.

Martin was able to buy and keep a handgun despite a felony conviction in Mississippi.

Human Resources Manager Clayton Parks, seen with his family, was killed when an employee opened fire the moment he was told he was being let go from the job

Vincente Juarez (second from left), a stockroom attendant and forklift operator, was killed

Josh Pinkard, left, the plant manager at the Henry Pratt Co. industrial valve manufacturing plant, was also killed when the shooter opened fire. Russell Beyer's sister Dawn posted a moving tribute after he was confirmed among the dead

He killed human resources manager Clayton Parks of Elgin; plant manager Josh Pinkard of Oswego; mold operator Russell Beyer of Yorkville; stock room attendant and fork lift operator Vicente Juarez of Oswego; and Trevor Wehner, a Northern Illinois University student who lived in DeKalb and grew up in Sheridan.

Martin was no stranger to police in Aurora, where he had been arrested six times over the years for what Ziman described as 'traffic and domestic battery-related issues' and most recently, for violating an order of protection in 2008.

After an initial background check failed to detect his felony conviction, Martin was issued his FOID card and bought the Smith & Wesson handgun on March 11, 2014.

Five days after that, he applied for a concealed carry permit. That background check, which used digital fingerprinting, did flag his Mississippi felony conviction and led the Illinois State Police to revoke his permit.