(CNN) — A gunman wounded five students at a suburban Cleveland high school Monday morning before being chased out of the building by a teacher, police said at a news conference.

The Chardon High School shooting suspect — believed to be a student, according to a school official — was in custody after turning himself in to bystanders, police said.

FBI Special Agent Scott Wilson declined to say how badly the students had been hurt in the incident in Chardon, Ohio, about 30 miles east of Cleveland.

“We just hope that they’re OK,” he said.

Two students injured in the shooting, one boy and one girl, were taken to Hillcrest Hospital, spokeswoman Heather Phillips said. One was in serious condition, the other in stable condition, she said.

Three students were taken by helicopter to MetroHealth Medical Center, hospital representative Shannon Mortland said in a statement. Mortland did not provide details on their conditions.

A student at Chardon High, Evan Erasmus, told CNN affiliate WEWS that the victims may have been students at another school in nearby Auburn, Ohio, waiting for a bus to take them there.

He said the suspect may have posted a threatening message on the social networking service Twitter before the shooting.

“I think he said that he was going to bring a gun to school, and I think that everyone just blew it off like he was joking,” Erasmus said.

Police recovered a handgun and gave it to the federal Bureau of Alcohol, Tobacco, Firearms and Explosives for examination, the agency said.

A law enforcement source said the Geauga County Sheriff’s office and federal agents were executing search warrants in the case, but the official did not provide locations.

One student told CNN affiliate WKYC that he heard what he thought at first was firecrackers.

“Then I saw a bunch of people running out, so I started running,” said the student, whose name was not available. “I heard someone yell behind me, ‘Get down.'”

The boy’s mother said she was terrified.

“I had just dropped him off at the school, and not even 10 minutes later, I got a text from him saying there was a shooting at the school,” she said.

Investigators took over the school Monday morning and were collecting evidence after students had been evacuated to nearby Maple Elementary School, said Lt. John Hiscox of the sheriff’s office.

He declined to say how authorities learned of the shooting.

School administrators called off school for the day and assured parents that students were safe.

Still, parents eager to retrieve their children hurried to school buildings, forming long lines as school officials and police checked identification before releasing students. SWAT team members stood guard outside the school, allowing only a few parents inside at a time, enhancing what was a surreal scene for many.

“This stuff doesn’t happen here at Chardon. Everybody’s a little upset,” said one parent who was preparing to pick up his daughter, a 10th-grader who had been evacuated to Maple Elementary School.

Parents and children frequently embraced and cried when reunited.

Teresa Hunt said she exchanged about 50 texts with her 18-year-old daughter, a senior at the high school. They began about 7:45 a.m., minutes after the shooting was reported. Hunt said her daughter hunkered down with her class inside their classroom, staying clear of the door. She said they could hear police officers running down the hall.

“They’re terrified. She was crying. Her anxiety was way up,” Hunt said.

“I did ask her, about the third or fourth text in, if she had any indication that something was going to break out,” Hunt said. “She said, ‘No, this was sudden. I had heard nothing.’ Her friends had heard nothing also.”

Erasmus said he believed that frequent shooting-situation drills and the quick response of school authorities helped keep the situation from becoming worse.

“We’re not that kind of place where it happens, so it’s really shocking,” he said.

Police were not releasing information on the suspect Monday, but Superintendent Joseph Bergant said the suspect is a student.

There is a long history of deadly violence on school campuses, ranging from incidents in which students stab each other or shoot staff members to mass murders like the ones at Virginia Tech and Columbine High School.

In April 1999, two teenagers, Eric Harris and Dylan Klebold, killed 12 students and a teacher before they killed themselves in the library at Columbine High School in Littleton, Colorado.

Gunman Seung-Hui Cho unleashed one of the deadliest campus attacks in American history at Virginia Tech in April 2007, killing 32 students and staff members. Two handguns were found near his body after the 23-year-old senior finally ended his rampage by killing himself.

Not all school killings are carried out by students. A 32-year-old man, Charles Roberts IV, took 11 girls hostage at a small Amish school in Pennsylvania in October 2006 and killed five of them. The other six were wounded before Roberts killed himself.

 — CNN’s Melissa Gray, Chuck Johnston, Richard Greene and Carol Cratty contributed to this report.