A former Border Patrol agent was sentenced to more than four years in a federal prison for gun-smuggling Thursday.

Ricardo Montalvo, 28, has been behind bars since April after a year long investigation found he was buying firearms that would illegally be exported to Mexico.

Montalvo, 28, pled guilty to the charges in August and was sentenced by Senior U.S. District Judge David Briones to 51 months in a low-security Federal Correctional Institution in Bastrop, Texas.

He will also pay a $100 fine and be on three years probation following his release.

Montalvo worked at the Ysleta port of entry and was arrested April 9, along with his girlfriend Carla Gonzales-Ortiz, on conspiracy, firearms and smuggling charges. 

According to the indictment, the two illegally bought several firearms and ammunition between November 2010 and January 2011 with the intention of smuggling them across the border to be bought by Mexican cartels.

Some of the firearms and ammunition purchased included AK-47's, 20,000 round of ammunition and 97 high-capacity magazines along with 37 mm flare launchers. According to the United States Department of Justice, these items are desired by Mexican cartles.

Gonzales-Ortiz also pleaded guilty to being his accomplice. In her plea agreement, she admitted that she knew Montalvo was committing a federal offense and that he was using her and others to make straw purchases of firearms but failed to report it. 

She could face up to three years in prison with the same fine of $250,000. After serving her sentence, she will also be deported because she is a Mexican national who was living in El Paso.