The elderly suspect in a Friday morning blast that rocked a Georgia law firm died in the explosion, according to investigators, but his motive was still unclear.

District Attorney Kermit McManus told FOX News that the man believed to have set off the bomb in the McCamy, Phillips, Tuggle & Fordham office in downtown Dalton is dead.

Investigators said later Friday afternoon that the person whose body was found was the 71-year-old man believed responsible. McManus told The Daily Citizen that the suspect is Lloyd Cantrell, but that wasn't immediately confirmed by police.

The bomber's motive is under investigation.

Lt. Bruce Frazier of the Dalton Police Department told reporters that police initially responded to some kind of disturbance at the small, northwest Georgia law firm before the blast.

An officer saw someone get out of a sport utility vehicle and run behind the building. The 10 a.m. explosion — which burned the clothes off one of the four injured and blew out windows — followed.

Justice officials told a local news station that it appeared as though an explosive device was thrown through the law firm's window.

Authorities placed an area school on lockdown.

Two of the wounded were treated at a hospital and released, one was admitted and a fourth — an attorney at the firm who suffered multiple burn injuries — was taken to a burn center in Augusta.

Footage from a robotic camera sent with search crews inside the law offices showed a man lying motionless on the floor, according to McManus. The suspect's body was still in the building Friday afternoon, police said.

Hours after the explosion, the office continued to smolder, with plumes of smoke shooting into the air. The eight-lawyer firm, founded in 1932 and specializing in personal injury and wrongful death cases, works out of a two-story, colonial-style house.

Frazier denied initial reports by the Citizen that officials had a man in custody and were questioning him.

City Park Elementary School was placed on lockdown and parents were told not to come to the building, according to local reports.

Steve Williams, an attorney at McCamy, said he was at the post office next door when he heard a loud explosion, according to the Citizen. He said he didn't know how many people were in the building at the time.

Police cordoned off the block and shut down the post office near the law firm.

Federal authorities from the Bureau of Alcohol, Tobacco, Firearms and Explosives were assisting local police in the investigation.

Dalton is 26 miles from Chattanooga, Tenn., and about 77 miles from Atlanta.

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FOX News' Harris Faulkner, Catherine Donaldson-Evans and The Associated Press contributed to this report.