A U.S. Border Patrol agent has been charged with murder in the fatal shooting of a Mexican illegal immigrant in January.

Prosecutors in the southwestern state of Arizona filed four charges Monday against agent Nicholas Corbett, including first-degree murder.

The charges say Corbett unlawfully killed Francisco Dominguez-Rivera January 12 as the immigrant crossed the Mexican border illegally into Arizona.

Corbett has said he fired at Dominguez-Rivera in self-defense after being threatened with a rock.

Prosecutors say evidence shows Dominguez-Rivera presented "no threat" to the agent. The evidence includes testimony from three Mexicans who tried to cross the border with Dominguez-Rivera.

The Mexican government has condemned the killing.

Corbett remains a Border Patrol agent but is no longer working in the field.

Some information for this report was provided by AP and Reuters.