As the debate on stricter gun controls is becoming a hot political issue, 11 people have died in two separate incidents.
In one, a wounded 11-year-old boy hid in a cupboard for eight hours in terror after a gunman killed his mother, aunt and four young relatives.
Santonio Briskey was the only survivor of a rampage which left seven dead in a house in Atlanta in a mainly black neighbourhood. One of the dead is believed to be the boyfriend of Santonio's mother and to be responsible for the murders.
The deputy police chief, Mr C.B. Jackson, said: "The possibility does exist that one of the persons inside, who is also deceased, is responsible for all the shootings and that the injury to himself was self-inflicted".
When Santonio emerged from the cupboard and approached a neighbour, Ms Georgia Hall, he told her that his stepfather had been responsible for the killings. "My stepfather shot my mama, my auntie, my brother, everyone," he said, according to Ms Hall.
Later in hospital, Santonio told his father, Mr David Lucas, that the shooting started after his mother had a confrontation with the man. "She told him she was ready to break it off," Mr Lucas told a local TV station. "I guess he couldn't take it."
Two of Mr Lucas's sons, aged 13 and eight, were among the victims.
Police were called shortly before 3 p.m. on Monday afternoon after Santonio, who was wounded in the elbow, went to neighbours for help.
He told the police the shooting started before 6 a.m.
Ms Betty Fuller, a neighbour, said that Santonio's mother had lived in the house with her sister and five children for three years. She said that the boyfriend, now believed to be the killer, had started coming around about a year ago.
Ms Fuller said that the mother was attentive to her children and friendly, always stopping to wave and chat, unless the boyfriend was around.
The police were unable to enter the house for several hours because of a pit bull terrier and a Rottweiler inside. Deputy Chief Jackson said: "As you can imagine, there are bodies in a number of rooms. There is quite a bit of blood". There was at least one gun in the house, he added.
Santonio was reported to be in a stable condition in the hospital.
Meanwhile, a man suspected of killing three teenage girls and his Bible study teacher in Sidney, Ohio, surrendered yesterday after a two-hour standoff with police at a filling station.
Mr Lawrence Michael Hensley (30) has been booked on four counts of aggravated murder, according to the Shelby County Sheriff, Mr Mark Schemmel.
Last Thursday the bodies of three teenage girls were found in Mr Hensley's home after a 22year-old woman, who had been shot, escaped from the house. Later Mr Brett Wildermuth, Mr Hensley's Bible teacher, was found shot dead at his home outside Sidney.
A local newspaper, the Dayton Daily News, has reported that Mr Hensley was convicted twice in four years for public indecency. His pastor, the Rev Ben Davis, said Mr Hensley had been involved in devil worship but was trying to mend his ways.
The police say they believe Mr Hensley killed the three girls and then drove with his wife, Julie, to Mr Wildermuth's house for a prayer session before killing him.