Missouri fugitive suspected of killing woman he kept locked in a box and her son
Mugshot for sex offender and kidnapping suspect James Horn, Jr. [KSHB-TV]

A Missouri woman who escaped captivity from a wooden box three weeks ago was found dead in a home on Thursday, along with her teenage son, and police are searching for the man suspected both of locking her up and killing her.

Officers found Sandra Kay Sutton, 46, and son Zachary Wade Sutton, 17, shot dead in a house in Clinton, Missouri, at about 4:20 a.m., according to a news release from the Clinton Police Department.

The bodies were found when family members returned to the house after work, police said.

On April 30, Sutton told police her former boyfriend, identified as James B. Horn Jr, 47, had routinely locked her in a box in their home in Sedalia, Missouri, over a four-month period.

Horn later was charged with kidnapping, armed criminal action and unlawful use of a weapon but has been at large ever since.

Clinton police said Horn is suspected in the killings in Clinton, about 45 miles from Sedalia.

"He is a dangerous person, an extremely dangerous, violent person," said Clinton Police Lieutenant Sonny Lynch.

The box in which Horn allegedly kept Sutton was 100 inches (2.5 meters) long, 45 inches (1.1 meter) wide and 52 inches (1.3 meter) tall, according to a detective's affidavit filed with the earlier charges in Missouri.

Sutton told authorities Horn forced her to help him build the box by wielding a long knife. She was locked in the box when he was not home, released when he got home from work and was compelled to have sex with him, authorities said.

Police on Thursday found a vehicle belonging to Sutton parked at a hospital in Sedalia near the home where he had kept Sutton captive, Lynch said.

Local police and Missouri State Highway Patrol officers stormed the house and nearby abandoned properties, said patrol operator April Lewis. Horn was not found and officers have left the scene, she said.

Zachary Sutton was a student at Clinton High School, according to a Facebook posting that said: "We are heartbroken over the tragic and senseless loss of Zach Sutton and his mother. Counselors are available at CHS."

Horn is a registered sex offender because of convictions in Tennessee in 1993, according to Missouri State Highway Patrol online court records. He later was convicted of kidnapping his estranged wife in Mississippi and served 10 years in federal prison, court records show.

(Reporting by Kevin Murphy; Editing by Fiona Ortiz, Alex Dobuzinskis and Sandra Maler)