The only other person shot, student Ella Whistler, was in critical but stable condition, according to her family. They released a statement saying they were still trying to process "what happened and why".

President Donald Trump sent a tweet thanking Jason Seaman "for his heroic act in saving so many precious young lives. His quick and automatic action is being talked about all over the world!"

Ethan Stonebraker, a student witness, said the shooter was acting suspiciously when he walked into the classroom while the class was taking a test on Friday. He told ABC News that Seaman, 29, threw a basketball at the shooter and ran toward the bullets as screaming students sought cover behind a table.

"If it weren't for him, more of us would have been injured for sure," the seventh grader said.

Jeremy Seaman told The Indianapolis Star that his brother was shot three times and underwent surgery. He said Jason Seaman was a defensive end for Southern Illinois University's football team and had never been a person to run away.

Investigators said the shooter had asked to be dismissed from the class before returning with two guns. He was arrested "extremely quickly" following the shooting around 9 a.m. Friday, local police Chief Kevin Jowitt said.

Authorities didn't release the student's name or say whether he had been in trouble before but indicated he likely acted alone. Police said the student didn't appear to be injured.

Australian Associated Press