A suspect in the 2003 murder of an off-duty Border Patrol agent traveling in Mexico is now in custody in an Arizona jail, Cochise County Sheriff Larry Dever told FoxNews.com.

The suspect, Jose Arturo Arreola-Lopez, 26, was booked Wednesday in Cochise County on an outstanding probation violation warrant. U.S. and Mexican law enforcement are currently negotiating his extradition to Mexico, where sources say he will face charges in connection to the killing of U.S. agent Jorge Luis Salomon.

“The murder occurred in Mexico. We are working diligently with Mexican authorities to assure that they get their crack at him if they have a prosecutable case,” Dever told FoxNews.com. “It was an exceptionally brutal beating of a U.S. law enforcement officer, so our federal partners on the U.S. side are deeply engaged, as well.”

On Feb. 24, 2003, Arreola-Lopez was found guilty of marijuana possession in Cochise County court, sentenced to time served and probation and released into the custody of Border Patrol on an immigration detainer, Dever said.

"He went back to Mexico but he violated our probation here because he didn't check back in with the court, so a felony warrant was issued for his arrest," Dever said. "Four days after he got back to Mexico, (Salomon) was killed."

Border Patrol did not immediately return FoxNews.com's request for comment.

An attorney for Arreola-Lopez could not be reached.

Salomon, 23, was visiting relatives in Mexico in February 2003 when he met four local men and went out drinking with them. When the men discovered that Salomon was a Border Patrol agent, they reportedly attacked him, beating him to death before stealing his vehicle and a gold necklace he was wearing.

Francisco Javier Rosas Molina, an 18-year-old Mexican national was arrested in connection to the murder, and Mexican authorities informed U.S. law enforcement that the three other suspects were likely headed north in an attempt to evade capture for their role in Salomon's murder. 

During the Mexican government investigation, it was determined that Arreola-Lopez was one of the three outstanding suspects in the murder case and a warrant was issued in Mexico for his arrest.

On April 20, 2011, during a routine warrant check by Cochise County Adult Probation, county officials discovered that Arreola-Lopez was in custody in St. Paul, Minn., on a separate local charge under a slightly different spelling of his name, Dever said. Cochise County took custody of him on Wednesday.