Police Superintendent Eddie Johnson said during a news conference “the community needs some answers and they need them now” as a reason to release the 30-second clip within 24 hours of the shooting.
“We will be as transparent as possible...while respecting” the Civilian Office of Police Accountability’s (COPA) investigation of the incident, Mr Johnson said.
The video was released quickly to try and quell the community’s anger over Mr Augustus’ death - one in a long line of young, black men killed by police in controversial circumstances across the country in recent years.
Mr Johnson also offered his condolences to Mr Augustus’s family, with whom he said he had consulted before the video release.
He also said the officers made a “split second” decision based on maintaining not just their safety, but that of the innocent people surrounding the scene of the incident.
Mr Augustus appeared to be running away from police in the video. At one point he spun around and reached to his waist, where it can be seen he had what looked like a gun in a holster.
However, in the slow motion version of the video released alongside the real-time clip, Mr Augustus appeared to reach for his wallet when officers approached him.
The footage pauses and zooms in on the weapon, which police spokesman Anthony Guglielmi said was done to ensure what appeared to be a semi-automatic handgun in its holster and two bullet magazines tucked into Mr Augustus' waist could be seen clearly.
Police said they had approached the 37-year-old on Saturday evening because they were suspicious of the “bulge around his waistband", patrol chief Fred Waller said.
He had been leaving his job as a barber at the nearby Sideline Studio and Beauty Salon when a witness Gloria Rainge told the Chicago Sun-Times said Mr Augustus, known as “Snoop” in the neighbourhood, was told by police officers not to sell loose cigarettes.
Ms Rainge said Mr Augustus explained he was not doing that, but the situation escalated and in the ensuing scuffle “a card protrudes from his wallet. It appears to be a Firearm Owners Identification Card, which allows qualified people to buy weapons and ammunition,” the Washington Post reported.
He was shot as he was running away and turned around to face the three officers who had tried to grab his arms.
Mr Johnson later confirmed Mr Augustus did not have the correct permit to carry a concealed weapon, however he did not say whether police officers pursuing him were aware of that or if the card that appeared to be a permit in the video was the specific license required.
The officers involved have been put on 30 days of administrative leave and further action will be taken as COPA carries on its investigation. Their names have not been made public as yet.