PERRY, Iowa - A teen armed with a shotgun and a handgun unleashed terror at an Iowa high school on the first day of classes in the new year, authorities said, killing a sixth grader and wounding five others as people hunkered down in classrooms, barricaded offices and fled the bullets.

The suspect, a 17-year-old student at the school in Perry, died of what investigators believe was a self-inflicted gunshot wound, an Iowa Division of Criminal Investigation official said. An administrator, later identified by his alma mater as Perry High School Principal Dan Marburger, was among the five wounded Thursday as students returned from winter break.

Authorities identified the shooter as Dylan Butler, 17, but provided no information about a possible motive. Two friends and their mother who spoke with The Associated Press said Butler was a quiet person who had been bullied for years.

Authorities said Butler had a pump-action shotgun and a small-caliber handgun. Mitch Mortvedt, the state investigation division’s assistant director, said during a news conference that authorities also found a “pretty rudimentary” improvised explosive device and rendered it safe.

The suspect’s motive was being investigated and authorities were looking into “a number of social media posts” he made around the time of the shooting, Mortvedt added.

A law enforcement official briefed on the investigation said federal and state investigators were interviewing Butler’s friends and analyzing Butler’s social media profiles, including posts on TikTok and Reddit.

Shortly before Thursday’s shooting, Butler posted a photo on TikTok inside the bathroom of Perry High School, the official said. The photo was captioned “now we wait” and the song “Stray Bullet” by the German band KMFDM accompanied it. Investigators have also found other photos Butler posted posing with firearms, according to the official, who was not authorized to publicly discuss details of the investigation and spoke to AP on condition of anonymity.

Sisters Yesenia Roeder and Khamya Hall, both 17, said alongside their mother, Alita, that Butler was bullied relentlessly since elementary school, but it escalated recently when his younger sister started getting picked on, too. His parents brought it up to the school, they said, and that was the “last straw” for Butler.

“He was hurting. He got tired. He got tired of the bullying. He got tired of the harassment,” Yesenia Roeder Hall, 17, said. “Was it a smart idea to shoot up the school? No. God, no.”