MARTINEZ (CBS SF) — A Contra Costa County gang crackdown, launched in 2016 and targeting violent Norteno gang members and their associates, has resulted in 15 individuals being convicted of felony offenses including attempted murder, transporting weapons and selling drugs, prosecutors announced Wednesday.

The Contra Costa County District Attorney’s Office released the final tally as they shut down Operation Omega Red — a law enforcement effort consisting of officers from the Concord Police Department, FBI agents and other partner agencies.

Prosecutors said the most dangerous individuals — Thomas “Lil T” Leon and Armando “Mando” Amaro — received 35-year sentences in prison each. Other violent offenders including Jesse “Manos” Loyola were sentenced anywhere from 25-to-18 years in prison.

In all, over 165 years of custody time resulted from the Omega Red prosecutions.

“We focused our efforts on the violence drivers – the individuals who were committing the most serious acts of violence and putting the community in the greatest danger,” said Contra Costa County District Attorney Diana Becton.

Between July of 2015 and June of 2016, there were 11 shootings between the notorious Nortenos and Surenos gangs in the central and eastern parts of Contra Costa County. Seven of these shootings resulted in homicides.

Four of those murders occurred on Highway 4, two occurred in Concord and one took place in Bay Point. Concord Police and other law enforcement agencies believed these shootings were related to an ongoing gang war between the two rival gangs.

The task force began a strategic investigation targeting the most violent Norteno gang members suspected of participating in the shootings. The investigation lasted just under three months and resulted in the arrest of over 20 individuals; 18 of these individuals were later prosecuted for crimes ranging from conspiracy to commit murder, attempted murder, drug sales, witness retaliation and firearms crimes.

From the date of the initial arrests in this case in August of 2016, there has been one murder on Highway 4, which was not gang related, and there has only been one gang related murder in Concord.

“This drastic reduction from seven gang driven homicides in under one year to only one in the last three years is a testament to the effectiveness of this kind of targeted law enforcement action and the power of police partnerships across the county,” Concord Police Chief Guy Swanger said.