Police are searching for James Barton Horn Jr., seen above, after finding Sandra Kay Sutton, 46, and her son, Zachary Wade Sutton shot to death Thursday, May 21, 2015. AP

Sedalia police officers are on alert at a standoff in Sedalia, Mo.where police believe they have a suspect in the slayings of Sandra Sutton and her teenage son. Jill Toyoshiba/The Kansas City Star via AP Photo

It was less than a month ago that James Barton Horn Jr., 48, was charged with allegedly holding his ex-girlfriend Sandra Kay Sutton captive in a wooden box for months in western Missouri. Now, police have surrounded a house where Horn is believed to be hiding after Sutton and her son were found dead on Thursday.Sutton, 46, and her teenage son Zachary Wad Sutton were found dead inside a relative's home in Clinton, Mo. early Thursday morning. Both victims appeared to have been shot overnight while Sutton's relatives were at work, police said. Police say that Horn, who disappeared before police could arrest him, is "absolutely" a suspect in the deaths.Police have been on the hunt for Horn since he was charged earlier this month for kidnapping Sutton. Investigators claim that Horn had kept Sutton in a wooden box off-and-on for four months in the home they shared in Sedalia, Mo. Horn is a registered sex offender and previously served time in prison for a kidnapping and sexual attack.Sutton had told police in late April that Horn had threatened her with a tire jack after an argument in January. When the couple returned home, Horn then began building the wooden structure, and Sutton was ordered to help construct it.The box was kept in a bedroom and contained a bucket full of urine and feces, and measured 100 inches long, 48 inches wide, and 52 inches tall. The box also contained several layers of insulation, padding and sleeping bags, and a small air hole, according to police. Sutton was allowed to leave the box when Horn returned home from work, police said.Police have currently surrounded a home where they believe Horn may be hiding, but have not made contact with anyone inside as of late Thursday morning.