DALLAS (CBSDFW.COM) – A man who pled guilty last year to his role in a gun trafficking operation that was linked to the killing of a federal agent in Mexico was sentenced Monday to seven years in prison.

Otilio Osorio, 23, was arrested in February of last year and pled guilty to three charges, including making a false statement or representation and possessing a firearm that had its serial number removed.

According to court documents, Otilio and his brother Ranferi Osorio, 28, Kelvin Leon Morrison, 26, and Luis Carbajal, 23, conspired to buy guns from licensed dealers using false statements, which the dealer is lawfully required to record and store.

On Feb. 15, 2011, a member of a Mexican drug cartel fired one of those guns, a Romanian-made weapon similar to an AK-47, during an ambush.

U.S. Immigration and Customs Enforcement Agent Jaime Zapata was shot and killed during that attack, the first U.S. officer to die in the line of duty in Mexico since 1985.

On Oct. 10, 2010, Otilio purchased the weapon at a Fort Worth gun show. A month later, he and his brother were observed selling a 40 gun load to an informant at a store parking lot in Lancaster.

Federal records show that Bureau of Alcohol, Tobacco and Firearm agents were watching, but allowed the Osorio brothers to drive away after the deal.

Agent Tom Crowley, spokesman for the ATF in North Texas, told CBS 11 investigative reporter Jack Douglas in February that arresting the brothers then would’ve risked blowing a larger investigation.

“There was a stop, but it was also a part of another federal law enforcement operation … by taking them down and arresting them at that time would have possibly jeopardized that investigation,” Crowley said then.

In Febuary, Otilio’s brother Renferi was sentenced to 10 years in prison. Morrison received a 2 ½ year sentence while Carbajal received two years of probation.

The investigation was conducted by the ATF, the Drug Enforcement Administration, the FBI, ICE, Homeland Security, Lancaster Police and the Texas Department of Public Safety.

More From CBS Dallas / Fort Worth

Drip Pan: CBS Local App
Drip Pan: Weather App

Watch & Listen LIVE