A 14-year-old gunman opened fire at a high school in Cleveland, Ohio, shooting four people before committing suicide, local authorities said.
Cleveland Mayor Frank Jackson two students and two adults were wounded in the shooting at SuccessTech Academy.
"The shooter is a 14-year-old student from the school. He has committed suicide," Jackson said at a press conference.
A 17-year-old student who was shot in the elbow was expected to be released from hospital in the evening while a 14-year-old who was shot in the side will likely be held overnight for observation, he said. The two adults are in stable condition.
Local media reported the student, who was described as a loner, was frustrated after being suspended from school for getting into a fight on Tuesday.
He came to school early Wednesday and roamed through the hallways with a gun in each hand and shots were heard on two different floors.
Screams and panic filled the building, witnesses said. Some students and teachers rushed outside at the sound of gunfire while others hid in closets and under desks while police searched the multilevel building for the shooter.
"I know that dude was crazy, we just knew it — you know when people are crazy, come on, man," one student who fled at the sound of gunshots told CNN.
"He was in my class ... He always wore a trench coat."
The boy was described by other students as a loner and devil worshipper who had made jokes about shooting other students in front of teachers.
"I didn't think he meant it," another unidentified student told news station WKYC. "I thought he just said it because he wanted to be popular."
Frantic parents rushed to the school to get news of their children and many were told to wait until police had finished interviewing them. Several complained the school had recently denied requests to hire a security guard.
Cleveland school district head Eugene Sanders said counselors were on hand to help students and administrators were working to reunite students with their parents. A decision had not yet been made on when classes would resume.
It was just the latest in a spate of shootings over the past weeks.
In September, two 17-year-old students were wounded when they were shot by a gunman at Delaware State University.
On Tuesday, two people were killed and two others injured in a shooting at a workshop in Simi Valley, California, police said.
That shooting took place at a tire assembly shop in the city of 120,000 some 50 kilometres northwest of Los Angeles often listed among the country's safest communities.
And on Sunday, a gun-toting sheriff's deputy went on a rampage, killing his ex-girlfriend and five other youths at a house party in a small town in Wisconsin, authorities said.
The 20-year-old deputy and all those shot were all part of a close-knit group of friends, sources said.
The incident recalled the horrors eight years ago of the Columbine high school shooting in Colorado and a similar bloodbath at Virginia Tech earlier this year.
During the massacre at Columbine High School massacre in April 1999, two students, Eric Harris and Dylan Klebold, embarked on a shooting rampage, killing 12 students and a teacher, as well as wounding 24 others, before committing suicide.
That shooting led to a period of introspection across the United States as the country briefly contemplated the downside of its celebrated "gun culture" but in the end, failed to pass laws or make other changes that would have made firearms less available.
A similar reaction followed the shooting in April of this year of 32 people by mentally disturbed student Cho Seung-Hui at Virginia Tech University, who also turned his arm on himself.
The Federal Bureau of Investigation reported last month that more than 1.4 million murders, rapes, robberies and assaults were committed around the United States last year, or a violent crime every 22 seconds.
The number of victims of violent crime in the United States last year was the equivalent of the entire population of European Union member Estonia or the African state of Gabon falling victim to murder, rape, robbery or assault.
The rate of violent crime was up by 1.9 percent compared with 2005, with murders climbing by 1.8 percent to nearly 15,000 cases last year.