The Lake County (Ind.) Coroner's Office identified the body Tuesday morning as Kyrin Carter. The cause of death has not yet been determined.
About 8:15 p.m. Monday, officers received a call from a volunteer kayaker who said he found a body about 300 feet from where Carter went missing.
"It was happiness that I found him, that I could give the family closure. But finding his body - it hit me hard. I wasn't ready for it," said Eric Carter, the volunteer who discovered the body.
A dive team was able to remove the body from the river, officials said.
Hammond police said they will hold news conference regarding the recovery at 11 a.m. Tuesday.
Carter, who has autism, was last seen on Saturday, May 15. He and his family, who are from the Kansas City area, had been staying at the Best Western in Hammond as they visited relatives. Carter walked out of the hotel barefoot and in shorts while a relative slept.
Crews and volunteers have been searching ever since Carter vanished. On Friday, police said that they had found surveillance video showing Carter going into the river.
"He didn’t just vanish. It’s been over five days. You mean to tell me he ain't came out for food, water, nothing?" Leslie Carter said.
The Sun Times Media-Wire contributed to this report…