A Mexican man who crossed into the United States illegally has been indicted for second-degree murder in the shooting death of a U.S. border patrol agent last December, U.S. prosecutors said on Friday.

Manuel Osorio-Arellanes was arraigned in a Tucson, Arizona courtroom for second degree murder as well as conspiracy to assault a federal officer and firearms possession charges, the Justice Department said.

The death of the border patrol agent, Brian Terry, has led to criticism of the Obama administration by Republicans over what they say is poor security on the U.S.-Mexican border. Drug cartels have battled each other on the Mexican side for years.

Questions have also arisen as to whether the guns used in the shooting came from an U.S. undercover operation aimed at cracking down on weapons being smuggled across the border into Mexico.

Osorio-Arellanes was part of an armed group of illegal immigrants who had crossed into Arizona and exchanged gunfire with border patrol agents, according to U.S. prosecutors. Osorio-Arellanes was wounded in the firefight and arrested.

"Today's indictment is an important step in this case, but it is only a first step to serving justice on behalf of Agent Brian Terry, his family and the other agents who were with Terry and their families," said Dennis Burke, U.S. Attorney for Arizona, said in a statement.

Others were charged for the death, but those names remained under seal. U.S. prosecutors said the individual who is believed to have fired the fatal shot fled the scene and is still being sought.

"This is an active ongoing investigation that is making more and more progress every day," Burke said.

A trial date was set for June 17 in U.S. District Court in Tucson. If convicted of second degree murder, Osorio-Arellanes faces a maximum sentence of life in prison.

Reuters