A federal grand jury on Wednesday returned a four-count indictment against a man previously charged in connection with a bombing of a Southern California spa that killed his ex-girlfriend, prosecutors said.

Stephen William Beal, 59, faces charges including use of a weapon of mass destruction and malicious destruction of a building resulting in death, the U.S. Attorney's Office said.

Beal had been arrested shortly after the bombing last year, but explosives charges were dropped and he was freed when prosecutors questioned whether material found at his home constituted a "destructive device." Further testing and investigation led to Beal's re-arrest this month.

The May 15 bombing killed Ildiko Krajnyak, 48, and seriously wounded two female clients when she opened a box that erupted in a fiery explosion at the spa in the city of Aliso Viejo, about 50 miles (80 kilometers) south of Los Angeles.

Beal's lawyer didn't immediately return a call seeking comment Wednesday. He is being held without bail and is scheduled to be arraigned March 25.

Krajnyak had told friends she was afraid of Beal after he made threats following their breakup. Beal told investigators he felt betrayed when she told him she was in a relationship with another man, U.S. Attorney Nick Hanna said at a news conference March 4.

The explosion blew out a big chunk of the building and body parts were found in the parking lot.

Over nine months, investigators were able to make the case by piecing together fragments from the bomb they could connect to Beal, including a battery, a wire and boxes similar to the one that contained the deadly bomb.