The bodies were found in a rural industrial park area outside Columbus, Ga., where the family lived.
Police say Eddie Harrington kidnapped the children March 5. After their abrupt disappearance, the FBI issued a warning poster that could not have been more blunt.
"Harrington reportedly is suicidal, has violent tendencies and serious mental health issues," it said.
The bulletin mentioned reports that Harrington and the children's mother had been on rocky terms recently. Police say they examined letters left behind by Harrington that suggested he had plans to kill the children.
The children's mother, Agena Battle, said last week that she called Harrington's parents, who had not heard from him, before she called police to report him and the toddlers missing.
She added that she thought "he's at the end of his rope," but that she didn't blame him.
"Just bring the kids back," she said.
Battle also tearfully pleaded for help from the public at a press conference in Columbus last week.
"My daughters, Aliyah and Agena, are only 23 months old. My son, Cedrick, he is 3 years old, he's a 3-year-old boy," she said. "My children cannot take care of themselves. Please help me."
According to the Justice Department and missing children advocacy groups, the children in this case are among the roughly 69,000 kidnapped each year. The overwhelming majority, 82 percent, are abducted by family members.
Georgia issued an arrest warrant for Harrington for cruelty to children on March 6. Four days later, a judge in the U.S. District Court for the Middle District of Georgia issued an additional arrest warrant for unlawful flight to avoid prosecution.
