MINNEAPOLIS (WCCO) — A memorial service was held Saturday for the son of a St. Paul police sergeant who was found dead.

Officers found 22-year-old William Grahek shot inside of a residence Tuesday. He was taken to the hospital and pronounced dead, according to Duluth police.

Grahek grew up in Centerville and attended school at the University of Minnesota Duluth. He also served in the United States Army Reserve.

Police said earlier this week they have a person of interest in custody, and they have identified a possible motive for the shooting.