A Missouri woman who authorities said had been held captive in a wooden box for months before being freed about three weeks ago was found dead early Thursday, along with her 17-year-old son, from what appear to be gunshot wounds, police said.

Sandra Kay Sutton, 46, and her son, Zachary Wade Sutton, were found dead in a relative's home in Clinton where they recently had been staying, Clinton police Lt. Sonny Lynch said.

Lynch said both victims appear to have been shot overnight when Sutton's relatives were at work. Relatives found the bodies around 4 a.m., and autopsies are planned.

Police have been searching for her ex-boyfriend, James Barton Horn Jr., since he was charged with kidnapping this month. Lynch said the 47-year-old Horn is "absolutely" a suspect in the deaths.

Horn was charged earlier this month for allegedly keeping Sandra Sutton in a wooden box for four months at the home they shared in Sedalia, about 45 miles northeast of Clinton in western Missouri.

The Sedalia Democrat newspaper reported that police have had a home in Sedalia surrounded since before dawn Thursday, and believe Horn is inside. Sedalia police did not immediately return calls seeking comment. The Sedalia school district canceled all outdoor activities and evacuated an alternative high school near that house.

The Pettis County prosecutor's office did not immediately return messages seeking additional information about the case, including whether there had been any protective orders in place against Horn.

In late April, Sutton told police that Horn had threatened her in a car with a "tire jack" after an argument in January and that when they returned home he began building a wooden structure, and that she had to help with its construction, according to a probable cause statement filed by Sedalia police in the case.

The probable cause statement also said Sutton was allowed to leave the box in the evenings when Barton returned home from work.

Police said the box, which they described as 100 inches long, 48 inches wide and 52 inches tall, was kept in a bedroom and contained a bucket full of urine and feces. The box also contained several layers of insulation, padding and sleeping bags and a small air hole.