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Florida shooting suspect Nikolas Cruz had been expelled from school

PARKLAND, Fla. -- Nikolas Cruz, the 19-year-old man suspected of gunning down at least 17 people Wednesday at a Parkland, Florida, high school, had once been expelled from the school for disciplinary reasons, Broward County Sheriff Scott Israel said.

Hours after the gunman opened fire on students and staff near the end of the day at Marjory Stoneman Douglas High School, details began to emerge about the former student behind one of the 10 deadliest mass shootings in modern U.S. history.

Cruz was expelled from the high school for unspecified disciplinary reasons, said officials, who provided different spellings of Cruz's first name throughout the day.

Officials are examining Cruz's digital profile, which contained what Israel described as "very, very disturbing" content.

Cruz was taken into custody without incident in nearby Coral Springs after the shootings, according to Israel.

The suspect has been talking to investigators, according to a law enforcement source.

Police said Cruz was armed with multiple magazines and at least one AR-15 style rifle.

Law enforcement sources said the Bureau of Alcohol, Tobacco, Firearms and Explosives is tracing the.223 caliber, AR-15 style firearm used in the shootings.

Investigators believe the suspect pulled the school's fire alarm to draw people out and get a higher death toll, according to a law enforcement source.

There had been a fire drill at the school earlier in the day, leading some to believe at first that the afternoon incident was another drill, a student told WSVN.

"Everyone just started freaking out," the student said. "But then word started going around that it was shots and not just, like, something else, everyone just started running towards the canal."

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