DENVER, Colorado - August 12, 2008 - The Denver District Attorney's office has dropped its case against a man who was facing three years in prison for assault, after 9Wants to Know obtained and showed prosecutors a videotape of the man's arrest.

The Denver Police Department has also started an internal investigation.

On the video, which was shot outside Coors Field at the home opener of the Colorado Rockies game on April 4, undercover Denver Police detectives hit, kicked and choked John Heaney.

"They both unloaded on me and I started seeing stars and the whole thing was just bam, bam, bam after that," said Heaney. "Someone had a chokehold and they were all on top of me and I couldn't breathe and I thought I was going to die."

After three detectives had Heaney facedown on the ground with his hands behind his back, the video shows undercover Det. Michael Cordova pull Heaney's hair, lift up his head and slam it into the ground, breaking two of his teeth on the cement.

Heaney says he had to have two teeth capped.

"I didn't know my teeth were broken until I was spitting out loose pieces," he said.

Heaney was charged with second-degree assault on a police officer and criminal mischief after one of the officer's sunglasses was broken during the arrest. The officers claim Heaney rode his bicycle through a red light at 20th and Blake Streets and then punched Cordova in the nose.

Heaney, who didn't know the men were undercover police officers, says he only flipped Cordova's Rockies hat off of his head.

Heaney says he was biking past Coors Field on April 4 to visit his terminally ill mother in a nursing home nearby.

Detectives Cordova and James Costigan, both on the Denver vice-narcotics squad, were working undercover in a scalping ring. Although 9NEWS is naming the officers, we have chosen not to show their faces to protect their undercover identities.

A local sports TV crew was videotaping the opening day of the Rockies when they saw and videotaped the arrest.

"The thing that kind of made everybody gasp was when the officer took the back of the guy's head and shoved it to the ground on his face," said TV producer Greg Prinkey. "He was not resisting. It was totally uncalled for."

When Prinkey saw men beating Heaney, he ran in to stop the fight. The video shows that's when the officers yelled, "Hey, we're cops! Get the (expletive) out of here!"

Prinkey gave the videotape of the arrest to 9NEWS.

"Had I not been rolling the camera, and no one else was rolling the camera, it might have just been swept under the rug," Prinkey said.

Before the Denver detectives knew about the videotape, they wrote reports and were deposed in court about what happened. Both officers said Heaney was throwing "wild punches" at them, hit the officers in the face and chest and continued to attack them, even when they had him on the ground.

Under oath, Cordova and Costigan also denied knowing anything about Heaney's broken teeth.

Heaney's attorney Lonn Heymann asked Cordova in court, "Was there a point at which somebody slammed his face into the ground?"

Cordova answered, "Absolutely not."

"How did Mr. Heaney's front teeth get broken," asked Heymann.

Cordova replied, "I have not a clue."

"When you start seeing that the officers are making arguments that are directly contradicted by this videotape, it raises questions about how believable the police officers are," Heymann told 9NEWS.

The Denver Police Department did not interview any civilian witnesses in their investigation of Heaney's arrest. However, 9NEWS interviewed three witnesses who all say Heaney did not hit the officers.

"I never saw the bicyclist make any sort of swing at either of the officers," said videographer Jason Jewett.

"He definitely didn't start it, that's for sure," said Nick Heckman, a still photographer for MileHigh Sports Magazine, who took four pictures of the arrest.

A hospital report and X-rays of Cordova's nose show it was not bleeding or broken after the arrest. Cordova claims it was red and swollen.

The Denver Police Department said Monday it is conducting an internal investigation of the arrest.

"The investigation is underway, and no conclusions should be drawn until all of the facts are available and the totality of the circumstances can be considered," said Division Chief of Investigations Dave Fisher. "Everyone in our country is initially entitled to a presumption of innocence, even police officers."

In addition to the injuries to his teeth, Heaney says he suffered neck and shoulder injuries.

Cordova and Costigan are still on duty while the investigation is underway. Once the police investigation is complete, it will be sent to the Denver District Attorney's office for review.