Nikolas Cruz, 19, was arrested about an hour after a shooting rampage at Marjory Stoneman Douglas High School in Parkland, Florida.
Broward County Sheriff Scott Israel told reporters that Cruz, who had been expelled from the school for reasons that have not been made public, was found with multiple ammunition magazines and one AR-15-style rifle.
“We already began to dissect his websites and the things on social media that he was on and some of the things that came to mind are very, very disturbing,” Israel said.
Chad Williams, 18, remembered Cruz as a troubled classmate from when they attended middle school together.
He said Cruz would set off the fire alarm, day after day, and finally got expelled in the eighth grade.
More recently, Williams saw Cruz carrying several publications about guns when they ran into each other at the high school.
“He was crazy about guns,” Williams said.
“He was kind of an outcast. He didn’t have many friends. He would do anything crazy for a laugh, but he was trouble.”
Jillian Davis, 19, said she was in a school Junior Reserve Officer Training Corps with Cruz in the ninth grade.
She remembered him as a quiet and shy young man who would almost change personality when angry.
He talked a lot about guns and knives but no one took him seriously, she said.
“I would say he was not the most normal or sane kid … he definitely had a little something off about him. He was a little extra quirky,” said Davis, who graduated from the school last year.
Maths teacher Jim Gard told the Miami Herald that Cruz had been banned from returning to campus while carrying a backpack.
“There were problems with him last year threatening students, and I guess he was asked to leave campus,” Gard told the newspaper in an interview.