At least six people - four women and two men - were freed. Around 31 people had remained on the bus throughout the terrifying ordeal, news agency AFP said in its report.
Heavily armed police including military and snipers had surrounded the bus as they negotiated with the gunman, who G1 news reported, had been armed with a gun, a tazer and gasoline.
The gunman as per reports boarded the Rio-bound bus at 5:30 am (0830 GMT) and began threatening passengers.
As per reports he was a young man wearing a white T-shirt and dark-colored trousers.
As per a military spokesman, the hijacker died at the scene. None of the hostages were injured, police said.
A live broadcast of the situation showed several ambulances parked near the bus, receiving hostages as they were released.
Around four hours later a sniper shot dead the hijacker.
Commuters stopped on the bridge could be seen standing outside their cars and taking photos with their smartphones.
Rio state Governor Wilson Witzel tweeted that he was following the situation and was in direct contact with the military police commander.
"The absolute priority is the protection of hostages," Witzel said.