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Denver, Colorado (CNN) -- The FBI said Tuesday it will look into an April 2009 beating of a man by Denver, Colorado, police, an incident that resulted in disciplinary action against two officers but no charges.
Denver Mayor John Hickenlooper requested the investigation Tuesday, arguing that a federal probe would "help ensure justice is appropriately served." Tuesday afternoon, the FBI said it would look into the matter, but said little else.
"As with any allegation that may fall within the FBI's purview, the Denver office will conduct a review of those events to determine if there is a basis for a federal civil rights investigation," the bureau said. "Per FBI policy, the Denver Division will not discuss ongoing investigative matters."
One of the two police officers involved received a three-day suspension and the other was docked a day's pay as a result of the incident, according to documents released by Denver officials Tuesday. In a statement released by his office, Hickenlooper said the video doesn't look good "when viewed in isolation," but that it "tells only a portion of the story."
The officers were disciplined for filing false reports after a review by the city's manager of safety, Ron Perea. But Perea said in a letter released Tuesday that the statements in their reports stemmed from "more of a misperception" than a "willful, intentional or knowing" attempt to deceive their superiors.
"Viewing the video alone is inflammatory," Perea wrote. "However, when the entirety of the situation is reviewed as it should be, I believe I made an appropriate disciplinary decision."
Despite that finding, the city's independent monitor is now calling for the officers to be fired.
"It was clear to me they were trying to cover up what actually happened and make it look better than it was," said Richard Rosenthal, who reviews police internal investigations, told CNN affilliate KMGH.
And Michael DeHerrera, the 24-year-old man seen being taken down and struck in the video footage recorded by a police camera, said Monday that he also wants the officers to lose their jobs.
"I think they should be fired, and if not, prosecuted for assault," DeHerrera said. "I think if any one of us had done these actions and assaulted someone, we would all be in jail."
The scene was captured by a street surveillance camera located across the intersection from where the beating took place. On the video, DeHerrera is seen talking animatedly on a mobile phone while police officers kneel over a friend who was being arrested on charges of punching an off-duty officer working security at a bar. The friend was being thrown out of the bar when the altercation occurred, according to police reports.
Another officer who responded the fight confronted DeHerrera, who was on the phone with his father, a veteran police officer. Soon afterward, the officer grabs DeHerrera by the head and shoves him to the pavement, and the camera pulls away seconds later.
DeHerrera's father, Anthony DeHerrera, told HLN's "Prime News" that Denver police mishandled the situation.
"Officers have so many tools on their belts nowadays, there is no reason to take somebody down the way they did," said the elder DeHerrera, a veteran sheriff's deputy in southern Colorado's Pueblo County.
He said he could hear sirens in the background while he was on the phone with his son, "so I felt law enforcement was arriving and everything going to be OK," he said. "And then I heard somebody in the background say 'Drop the phone,' and some obscenities. The next thing I hear is a thud. Then Michael was not talking anymore, so I knew it was Michael that got hit."
He said he yelled his son's name into the phone for about seven minutes, but, "All we could hear was cussing in the background and some thuds."
The younger DeHerrera had a bloody nose and a cut above his left eye when a police sergeant questioned him after the incident, according to the sergeant's report. He admitted to grabbing police officers he said were struggling with his friend, but denied attempting to punch anyone.
"I was already handcuffed, and every time I was trying to tell them what happened, they hit me," he told the sergeant, according to the report.
And witness statements found both men shoved the police officer seen in the video while they were across the street and out of view of the camera, Perea wrote.
"While there can certainly be debate whether the force was excessive or inappropriate, looking at all available evidence I do not believe excessive or inappropriate force could be proven," Perea added.
According to KMGH, charges against DeHerrera and a friend at the scene were dropped, and both men received a monetary settlement from the city.
Hickenlooper, a Democrat now running for Colorado's governor, said it was "appropriate for the independent monitor to question the manager of safety's decision" in the case.
"Very few cities have this type of check-and-balance system that we have created in Denver," Hickenlooper's statement said. "Even still, we are asking for a federal review of the matter."
CNN's Jim Spellman contributed to this report.