FILE PHOTO - Police officers guard an intersection after officer-involved shooting in Harrisburg, Pennsylvania, U.S., January 18, 2018. REUTERS/Daniel Shanken

HARRISBURG, Pa. (Reuters) - A deputy U.S. marshal who was killed in January while trying to serve an arrest warrant in Pennsylvania died by “friendly fire,” the U.S. Marshals Service said on Thursday.

Christopher Hill, 45, was accidentally struck by a bullet fired by another member of the law enforcement team serving an arrest warrant on Shayla Lynette Towles Pierce, 30, at a Harrisburg home for threatening a neighbor with a firearm.

When deputy marshals and local police announced themselves and entered the house, they were fired on by Kevin Sturgis, 31, who also was wanted by authorities on charges he shot his pregnant ex-girlfriend in Philadelphia.

Investigators initially believed that Sturgis, who was shot and killed as he tried to flee from the house, had fired the bullet that killed Hill.

“Today, the preliminary FBI forensics and ballistics review indicates that the round which struck Deputy Hill was fired by a fellow law enforcement officer who was engaged in a gun battle with the assailant,” the U.S. Marshals Service said in a statement.

The bullet passed through a wall in the home and struck Hill. He was pronounced dead in hospital. Sturgis did fire bullets that struck two other officers, causing injuries that were not considered serious, officials said.

Michelle Coghill, a spokeswoman for the U.S. Marshals Service, said the FBI report will be reviewed to determine “whether there are any lessons to be learned” and re-emphasized in training.

U.S. Marshal Martin Pane in Scranton, who was Hill’s boss, told Reuters that the slain deputy would still be alive if not for the “cowardice” that Sturgis showed in failing to face the Philadelphia charges against him.