A Missouri man accused of holding his former girlfriend captive in a crate at their home then shooting and killing her and her teenage son, was shot and killed Saturday, authorities.

Law enforcement officers killed James Barton Horn Jr., 47, at a state wildlife area in western Missouri, Sheriff Kent Oberkrom said.

Authorities had been searching for Horn since April when he was charged in the kidnapping of 46-year-old Sandra Kay Sutton. Prosecutors said Sutton told police that Horn kept her in a wooden crate off-and-on for four months at their at their Sedalia home.

Sutton and her 17-year-old son, Zachary Wade Sutton, were found dead Thursday at a relative’s home in Clinton, about 45 miles from Sedalia, where she had moved after escaping the home she shared with Horn.

Oberkrom said officers found Horn hiding in a closet in an abandoned building at the J.N. Turkey Kearn Memorial Wildlife Area. He said officers were led to the area by a tip they received Saturday morning.

When officers ordered him to surrender, Horn threatened the officers with a handgun, said Sgt. Bill Lowe, spokesman for the Missouri State Highway Patrol. It was unclear if Horn fired his weapon, Lowe said.

The investigation will focus on matching the weapons Horn had with him with the evidence taken from the scene of the Sutton’s murders.

Horn’s death was a major relief for the community, Oberkrom said.

"A lot of folks are very scared of this individual," he said. "There's a huge amount of relief.

Horn, a former Marine, allegedly locked Sutton inside the box whenever he was leaving the house. The box was 100 inches long, 48 inches wide and 52 inches tall. It was kept in a bedroom and contained a bucket full of urine and feces along padding and sleeping bags and a small air hole.

Police on Friday announced a $5,000 reward for information leading to Horn's arrest.

Horn served about three years in prison in Tennessee in the early 1990s in connection with a kidnapping and sexual attack. Records also show he pleaded guilty in 1997 in Mississippi to unlawfully kidnapping and abducting his estranged wife. He was sentenced in that case to 12 years and 11 months in prison, plus five years supervised release.

Federal prosecutors sought to extend Horn’s prison sentence by having certified as a “sexually dangerous” person.

Under the Adam Walsh Act, for Horn to be civilly committed for more prison time, federal prosecutors were required to prove several factors, including that mental illness would make it difficult for Horn to refrain from sexually violent conduct if released, according to court documents filed in the case.

Horn was diagnosed in 1991 with explosive personality disorder and narcissistic personality disorder, as well as major depressive disorder.

U.S. District Judge W. Earl Britt of the Eastern District of North Carolina, said prosecutors failed to reach that standard.

Horn was released from prison in December 2011, and his probation jurisdiction was transferred in 2012 to Missouri, according to online court records. He was still under federal supervision when he was charged with kidnapping Sutton.

The Associated Press contributed to this report