The 8-year-old boy is hospitalized and is expected to survive the Wednesday attack, said Don Bass, chief deputy with Hancock County sheriff's office on the Mississippi coast.
Bass said the older brother, with his throat cut, escaped the suspect's trailer Wednesday evening and ran about 500 yards to a neighbor's house. The neighbor called police.
The children were abducted Wednesday afternoon from a residence in Pearl River County and taken to the trailer in rural Hancock County where he sexually abused both boys, Hancock County Sheriff Ricky Adam said in a news release.
Bass identified the suspect as James H. Smith, 41. Smith was released from prison to house arrest in June after serving a few months of a lengthy sentence in a racketeering case involving methamphetamine and assaulting a police officer, according to corrections officials and court records.
It was not immediately clear whether Smith had a lawyer. An attorney who represented him in the racketeering case did not immediately respond to a phone message Thursday.
He was being held on a $3.5 million bond, Bass said.
Shane Tucker, chief deputy with Pearl River County sheriff's department, said Smith is a cousin of the boys' father's live-in girlfriend. He said Smith had not been around the boys much, but was familiar with them, and lured them away while they played in the yard.
After the older child escaped Smith's trailer, Bass said Smith grabbed the younger boy, put him in a car and was trying to get away when Hancock County sheriff's deputy Tommy Bethea spotted them and blocked the car's path. The suspect jumped out of his car and Bethea was able to rescue the 5-year-old, Bass said.
Authorities said the older boy's escape and the information provided by his brother were instrumental in their survival and the case against the suspect.
"Those boys did an amazing job," Tucker said.
Bass said Smith tried to get away by running through thick woods but was caught about 8 p.m. a few miles away on a highway. Smith hurt himself somehow in the woods and was treated for injuries, Bass said.
The 8-year-old was airlifted to a hospital in Mobile, Ala., and was in stable condition on Thursday, Adam said.
Smith has a lengthy criminal record. Tara Booth, a spokeswoman with the Mississippi Department of Corrections, said Smith was sentenced to more than four years in 2006 for receiving stolen property. His probation was revoked in January 2011 for failure to report and pay fines, and he was sentenced to more than two years.
He was sentenced in February to 20 years in the racketeering case, with five years to serve and 15 years on supervised release. But the court also ordered that Smith could be released to house arrest after completing a drug and alcohol program, according to court records.
He was released to house arrest June 19, Booth said.
"It's a shame," Tucker said. "If he had been serving his sentence, he wouldn't have been free to commit this crime."