One sixth grader was killed and five other people were wounded in a shooting inside a small-town Iowa high school early Thursday as students prepared to start their first day of classes after their annual winter break, authorities said.

"This strikes at the heart of everything that we hold dear. this senseless tragedy has shaken our entire state to the core," Iowa Gov. Kim Reynolds said at a press conference on Thursday afternoon. "It's impossible to understand why anything like this happens. But again, I want you to know that we'll work tirelessly to get the answers so that we can prevent it from happening again."

Police found the suspect in the shooting in Perry, Iowa, dead with what appeared to be a self-inflicted gunshot wound in the school soon after and an improvised explosive device was disarmed, said Mitch Mortvedt, an assistant director with the Iowa Division of Criminal Investigation, at the afternoon press conference.

Among the five surviving victims, four were students and the fifth was an administrator. As of Thursday afternoon, one was in critical, but not life-threatening condition, according to Mortvedt.

The shooter has been identified as 17-year-old Dylan Butler, a student at the high school. Police said Butler was armed with a pump-action shotgun and a small caliber handgun, and made threatening posts on social media.

"All evidence thus far suggests that Butler acted alone," Mortvedt said. He added there was no evidence to indicate the attack was related to race or ethnicity, but a motive had not yet been established.

The shooting began during a breakfast program prior to classes beginning. The explosive was "pretty rudimentary," according to Mortvedt, and "rendered safe" by state fire officials and agents with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

Two gunshot victims were taken by ambulance to Iowa Methodist Medical Center in the state capital of Des Moines, a health system spokesperson said. Some other patients were transported to a second hospital in Des Moines, a spokesperson for MercyOne Des Moines Medical Center confirmed, declining to comment on the number of patients or their statuses.

Dallas County Sheriff Adam Infante said during a news briefing earlier on Thursday morning that law enforcement received reports of the shooting at 7:37 a.m. local time and the first officer arrived on the scene within minutes. Mortvedt confirmed that timeline later in the day.

“School didn't start yet. Luckily, there was very few students and faculty in the building, which I think contributed to a good outcome in that sense,” the sheriff said.

The sheriff said he believes all students have been reunified with their families. 

Perry has about 8,000 residents and is about 40 miles northwest of Des Moines, on the edge of the state capital's metropolitan area. It is home to a large pork-processing plant, and low-slung, single story homes spread among trees now shorn of their leaves by winter. The high school and middle school are connected, sitting on the east edge of town.

High school senior Ava Augustus said she was in a counselor's office, waiting for hers to arrive, when she heard three shots. She and other people barricaded the door, preparing to throw things if necessary, with a window being too small for an escape.

“And then we hear ‘He’s down. You can go out,’” Augustus said through tears. ”And I run and you can just see glass everywhere, blood on the floor. I get to my car and they’re taking a girl out of the auditorium who had been shot in her leg.”

In Washington, U.S. Attorney General Merrick Garland was briefed on the shooting. 

FBI agents from the Omaha-Des Moines office are assisting with the investigation led by the Iowa Division of Criminal Investigation. The Iowa State Patrol is also among the agencies assisting.

The shooting occurred in the backdrop of the Iowa caucuses and not far from where Republican candidates were campaigning. GOP candidate Vivek Ramaswamy had a campaign event scheduled in Perry at 9 a.m. about a 1 1/2 miles from the high school but canceled it to have a prayer and intimate discussion, a spokesperson said. Ramaswamy offered prayers for the community on social media.

An enormous number of emergency vehicles surrounded the building that houses both the town's middle school and high school.

Zander Shelley, 15, was in a hallway waiting for the school day to start when he heard gunshots and dashed into a classroom, according to his father, Kevin Shelley. Zander was grazed twice and hid in the classroom before texting his father.

Kevin Shelley, who drives a garbage truck, told his boss he had to run. “It was the most scared I’ve been in my entire life,” he said.

Rachael Kares, an 18-year-old senior, was wrapping up jazz band practice when she and her bandmates heard what she described as four gunshots, spaced apart.

“We all just jumped,” Kares said. “My band teacher looked at us and yelled, ‘Run!’ So we ran.”

Kares and many others from the school ran out past the football field, as she heard people yelling, “Get out! Get out!” She said she heard additional shots as she ran, but didn’t know how many. She was more concerned about getting home to her 3-year-old son.

“At that moment I didn’t care about anything except getting out because I had to get home with my son,” she said.

Erica Jolliff said that her daughter, a ninth grader, reported getting rushed from the school grounds at 7:45 am. Distraught, Jolliff was still looking for her son Amir, a sixth grader, one hour later.

“I just want to know that he’s safe and OK,” Jolliff said. “They won’t tell me nothing.”

Jasmine Augustine, 18, was at the high school shortly after everything happened Thursday morning. She said she was dropping off a friend at the high school and his brother, who goes to the town's elementary school about a mile away.

“I was at Casey’s convenience store and saw one car speed by. I thought it was just someone getting pulled over," she said.

Augustine said that when she pulled in at the high school, someone told her there was an active shooter “and then we hurried up and left.”

“After that, there’s just tons and tons and tons of cops who came,” said Augustine, whose sister attends the high school but wasn’t near what happened. Jasmine and her dad picked up her sister from the armory afterward.

Linda Andorf, board president of the Perry Community School District, told NBC News: “It is horrendously awful. People need to figure out their life. This is just disgusting. It's terrible."

The high school is part of the 1,785-student Perry Community School District. The town of Perry is more diverse than Iowa as a whole, with census figures showing that 31% of the residents are Hispanic, compared to less than 7% for the state. Those figures also show that nearly 19% of the town's residents were born outside the U.S.

Republican Iowa Gov. Kim Reynolds wrote on X, formerly Twitter: “Our hearts are broken by this senseless tragedy. Our prayers are with the students, teachers & families of the Perry Community.”

Zach Nunn, who represents Perry in the U.S. House of Representatives, said in a statement that he is "beyond angry" about the shooting.

"My heart, and my commitment to holding those accountable, is with the community of Perry,” said Nunn, a Republican. “We have a duty to protect our children, families, and educators. … We will not rest until there is full accountability for this heinous act of violence.”

U.S. Sen. Chuck Grassley, R-Iowa, wrote on X, formerly Twitter, “Todays appalling violence at Perry HS is heartbreaking,” adding that he believes the Perry community is strong and will band together through a difficult time.

As of July 2021, Iowa does not require a permit to purchase a handgun or carry a firearm in public, though it mandates a background check for a person buying a handgun without a permit.

This is a developing story. Check back later for further updates.