An elementary school student was killed while five others were injured after a 17-year-old gunman attacked Perry High School in the town of Perry, Iowa, in the United States on Thursday.

According to the New York Times, the gunman, identified as Dylan Butler, who is also a student at the school, carried out the attack just before classes began when students from various grades had gathered for a breakfast programme.

Emergency calls about someone with a gun started to come in around 7:30 a.m., and approximately seven minutes later, emergency responders arrived, Mitch Mortvedt, assistant director of the Iowa Division of Criminal Investigation, said.

However, he had already killed a sixth-grade student and injured four students and one administrator before authorities could intervene. The attacker also died from a self-inflicted gunshot wound.

The identities of the victims remain undisclosed.

The gunman was equipped with a pump-action shotgun and a small calibre handgun, and a “rudimentary” improvised explosive was found.

Authorities are yet to determine the motive behind the shooting as police and other relevant agencies have commenced their investigation into the incident, including posts made on social media by the attacker during the act.