"He was determined. He knew what he was doing," said Alexandria Caporali, who grabbed her stunned friend and ran into a classroom as their classmates hit the floor.

"It was one right after another -- bang bang bang bang bang," she added. "You could see his arm jerking as he was pulling the trigger."

Police led a teenager away in handcuffs minutes later, and said the suspect will be charged with murder. Authorities did not identify the gunman responsible for the nation's first fatal school shooting of 2018, nor did they release any details about a motive.

Kentucky State Police Lt. Michael Webb said detectives are looking into his home and background.

"He was apprehended by the sheriff's department here on site, at the school, thankfully before any more lives could be taken," Webb said.

Seventeen students were injured, 12 of them hit with bullets and five others hurt in the scramble as hundreds of students fled for their lives from Marshall County High School. Many jumped into cars or ran down the highway, some not stopping until they reached a McDonald's restaurant more than a mile away. Parents left their cars on both sides of an adjacent road, desperately trying to find their teenagers.

"No one screamed. It was almost completely silent as people just ran," said Caporali, 16. "He just ran out of ammo and couldn't do anything else. He took off running and tried to get away from the officers."

The two fatalities were 15 years old: A girl died at the scene, and a boy died later at a hospital, Gov. Matt Bevin said, adding that all of the victims are believed to be students. Five young men, including three with gunshot wounds to head and one shot in chest, were flown about 120 miles (193 kilometers) to Nashville, Tennessee's Vanderbilt University Medical Center.

The attack marked the year's first fatal school shooting, 23 days into 2018, according to data compiled by the Gun Violence Archive, which relies on media reports and other information. The anti-violence group Everytown for Gun Safety has counted at least 283 shootings at schools since 2013.

The governor as well as several people in Benton said they couldn't believe a mass shooting would happen in their small, close-knit town. But many such shootings across the nation have happened in rural communities.

Marshall County High School is about 30 minutes from Heath High School in Paducah, Kentucky, where a 1997 mass shooting killed three and injured five. Michael Carneal, then 14, opened fire there about two years before the fatal attack at Columbine High School in Colorado, ushering in an era when mass school shootings have become much more common.

Meanwhile, in the small North Texas town of Italy, a 15-year-old girl was recovering Tuesday after police said she was shot by a 16-year-old classmate in her high school cafeteria on Monday, sending dozens of students scrambling for safety. Police in Louisiana, meanwhile, are investigating shots fired as students gathered outside their charter school.

"It's horrifying that we can no longer call school shootings 'unimaginable' because the reality is they happen with alarming frequency," said former Rep. Gabrielle Giffords, who survived being shot in the head in 2011. She called on Congress to strengthen gun laws.

Tuesday's shooting, moments before classes would have begun, disrupted some happy moments in the "commons" area of Marshall County High. Sixteen-year-old Lexie Waymon said she and a friend were talking about the next basketball game, makeup and eyelashes when gunshots pierced the air.

"I blacked out. I couldn't move. I got up and I tried to run, but I fell. I heard someone hit the ground. It was so close to me," Waymon said. "I just heard it and then I just, everything was black for a good minute. Like, I could not see anything. I just froze and did not know what to do. Then I got up and I ran."

Her friend, Baleigh Culp, told the AP in a Facebook message that they were joking and laughing until they heard a loud bang that sounded like someone's books hitting the floor.

"That's what i expected it to be, until i saw a body drop on the ground," Culp wrote. "There was bullets flying everywhere. I ran straight out the door and headed to the highway as fast as i could."