(NBC News) - The Justice Department on Tuesday is expected to announce its conclusion in the Trayvon Martin case, administration officials said. The government will not pursue federal civil rights charges against George Zimmerman in the shooting death of Trayvon Martin three years ago.

Zimmerman was acquitted of second-degree murder in the shooting. He said that he was acting in self-defense when he killed Martin, 17, during an altercation in a gated community in Sanford, Florida.

The shooting stirred a national debate about race and guns.