The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has traced a weapon used in the attack on ICE Special Agent Jaime Zapata to a Texas man.

A Romarm-Cugir Draco 7.62x39mm that was legally sold by a firearms dealer in the Dallas-Fort Worth area was transported to the Los Zetas cartel operators who used it to attack special agent Jaime Zapata and Victor Avila Jr. Agent Zapata was killed during the Feb. 15 ambush.

On Monday, ATF agents arrested three men in Texas believed to be responsible for trafficking weapons to the cartel.

Ranferi Osorio, 27, and his brother, Otilio Osorio, 22, were arrested at their home in Lancaster, Texas. Each is charged with possessing firearms with an obliterated serial number. 

An additional defendant, Kelvin Leon Morrison, 25, who lives next door to the brothers, is charged with knowingly making false statements in connection with the acquisition of firearms and dealing in firearms without a license.

The Romarm-Cugir Draco, a semi-automatic weapon, has been traced to Otilio Osario, who purchased it from Off Duty Enterprise in Joshua on Oct. 10, the ATF announced. Osario is charged with obliterating the gun's serial number, and initial ballistics tests show it was used in the attack, ATF Spokesman Tom Crowley tells POLICE Magazine.

A confidential informant from the ATF's Dallas office arranged a meeting with the Osorios and Morrison in early November, resulting in the seizure of 40 firearms with obliterated serial numbers, according to the ATF.

These guns have seen more frequent use by Mexican drug cartels, Crowley said.

"These are kind of new on the scene," Crowley said. "Gun dealers have access to them. We have techniques to raise serial numbers. It afforded us the opportunity to trace this to the Zetas."

Because of Mexico's strict yet mostly unenforced gun laws, drug cartels will pay as much as a 300 percent mark-up to purchase weapons on the black market. According to intelligence experts, weaponry smuggled to Mexican cartels arrive from a variety of sources that include the U.S., Guatemala, China, South Korea, and the Mexican military.

Related:

Six Zeta Cartel Members Arrested In ICE Agent's Killing

Cartel Operators Killed ICE Agent At Trafficking Checkpoint