DENVER -- Prosecutors announced a breakthrough in one of Denver's most high-profile murder cases Wednesday afternoon with a 39-count indictment naming a suspect in the shooting death of Broncos player Darrent Williams.

Denver District Attorney Mitch Morrissey said the indictment filed against 25-year-old Willie "Little Lett" Clark includes two counts of first-degree murder.

Morrissey said the investigation is still ongoing and called Wednesday's indictment a "step in the case." "This will continue to be an ongoing investigation," he said because police believe there is still another shooter at large.

Prosecutors would not comment on a second suspect, but said Clark is being charged as a principal in the case.

Clark is being charged with two counts of first-degree murder, 16 counts of attempted first-degree murder, 16 counts of crime of violence, two counts of second-degree assault and one count of illegal discharge of a firearm, Morrissey said.

Clark, who has a criminal record, is being held in federal custody without bond, Morrissey said.

He was arrested on a parole violation four days after William's death. He has long been considered a person of interest in the case.

"This indictment is the result of 18 months of some of the most intense investigation that I have ever seen in my last 25 years in this city," Morrissey said.

Williams' mother, Rosalind Williams, told The Associated Press the news brought her peace but that it was also "bittersweet" because it brought painful memories.

Williams, 24, was riding in a stretch H2 Hummer limousine with 16 other people, on northbound Speer Boulevard near 11th Avenue when the shooting happened on New Year's day 2007. The shots came from another vehicle, which sped away, police said.

Shooting Happened After Club Tussle

In addition to the charges, the indictment provided new insight into the slaying.

Williams and a group of friends went to the Safari Club to celebrate New Year's.

Another Broncos receiver, Brandon Marshall, and his cousin were partying with Williams' group that night and began spraying champagne around, "some of which hit a club patron and his friend, who confronted Williams and his entourage," Marshall told "Real Sports."

Those men flashed gang signs and were escorted out of the club, said members of a rap group from Williams' hometown of Fort Worth, Texas, who were with him that night.

Fellow teammate Javon Walker said he didn't see the encounter inside the club but saw trouble brewing when he left the club at closing time. Marshall and his cousin were exchanging heated words with two men, he said. The rappers said it was the same men who had been kicked out of the club earlier that night.

After Williams and Walker both tried to intervene, Williams told Walker to ride with him in his Hummer limousine, and they drove off into the night, Walker said.

Less than a mile away around 2 a.m., Walker said he was turning up the music when Williams suddenly fell into his lap.

Walker said he pushed Williams away and told him to quit messing around -- and that's when he saw blood spurting from Williams' neck and heard the other gunshots.

According to the indictment, Williams was shot in the neck by a .40 caliber bullet. Two other people inside the limo were also hit.

Walker said he held Williams close and tried to stop the bleeding.

"All I remember at that point in time was he was just looking up at me and I was just like, 'I got you, Dee, I got you, Dee. I got you, Dee,'" Walker recounted. "So, the limo went off the road into the side of the snow. I just remember grabbing him, pulling him out the limo."

Walker said he didn't know if he should run with Williams and worried if "these dudes were going to try to finish us off?"

"You don't know what to think," Walker said, "to have somebody die in your arms and you know you're the last person he hugged."

Investigators said at least 15 shots had been fired into the limousine.

A witness inside the SUV told police that Clark was driving and saw Clark "fire a handgun multiple times into the white limousine. The witness reported that he/she did not see anyone other than Willie Clark shoot from the SUV into the limousine," the indictment said.

This summer, detectives received a letter reportedly written by Clark in which Clark admitted to shooting and killing Williams.

According to the indictment, Detective Michael Martinez contacted Clark and "Clark admitted that he had written the letter."