A Cheektowaga man already in police custody on federal drug charges pleaded guilty Tuesday to first-degree manslaughter stemming from a 2016 killing.

Jeffrey Brown, 43, confessed to killing David Brown, 46, of Buffalo, in July 2016. The two men were not related.

"It turns out that the victim was dating the defendant's estranged wife," Erie County District Attorney John Flynn (D) said. He also says Jeffrey Brown's estranged wife brought the victim to a party at the defendant's mother's house. 

The prosecution wasn't sure they'd ever be able to prove that Jeffrey Brown committed the crime.

"No one at the party, none of the witnesses who were there were willing to cooperate," said Flynn.

But Jeffrey Brown was arrested on unrelated drug charges in November 2016. The U.S. attorney learned Brown had an excess of 700 grams of heroin with intent to distribute.

"That a significant amount. That's over half a kilo of heroin. That's a lot of heroin, so he was a significant drug trafficker in Buffalo," said U.S. Attorney James P. Kennedy.

Authorities say they knew he was the one who shot and killed David Brown at a party at Jeffrey's mother's house on July 3, 2016 and used the drug charge as leverage.

The U.S. Attorney's Office said they wouldn't resolve his drug charges until he admitted his role in David Brown's death, which he did Tuesday, pleading guilty to first-degree manslaughter.

"That courtroom was filled with members of the victim's family. This family would have never received closure. They would have never had their loved one's crime accounted for and someone held accountable for if not for this great cooperation," said Flynn.

The defense attorney and prosecutor said in court Tuesday they agreed to 17 years without parole on the manslaughter charge.

The U.S. attorney says the penalty for the conspiracy to possess with intent to distribute carries a penalty of ten years to life in prison and an up to an $8 million fine.

"There's commitment by the court that these charges are going to run concurrent with his federal sentence so that resolves both matters without doing additional time," said Anthony Lana, defense attorney.

Authorities say they hope this increased collaboration is something that will send a clear and strong message to both the community and these drug offenders.

"All we're trying to do is protect the community and do what we can do to do the best to get the longest sentence to keep these violent individuals off the streets," said Kennedy.

Buffalo Police Department Captain Jeff Rinaldo said, "It's making a difference in the fact that now communities, neighborhoods know there's going to voices that can listen. That there's going to be greater collaborations. That these crimes don't exist in a silo and they're not going to be treated as just a Buffalo problem or a county problem. They're going to be treated as a community issue."

Brown is set to be sentenced in April.