Cruz was arrested in Coral Springs, a neighboring city a few miles from the school, about an hour after fleeing the scene, the authorities said. He had slipped out of the building by mixing in with crowds of students.
The gunman had clearly prepared for the attack, U.S. Senator Bill Nelson of Florida said in an interview after speaking to the FBI.
“The shooter wore a gas mask, had smoke grenades, and he set off the fire alarm so the kids would come out of the classrooms,” said Nelson, citing details he learned from the FBI. Several students said they found it strange to hear the alarm, because they had already had a fire drill earlier in the day.
Sheriff Israel said he didn’t know the gunman’s motive but that law enforcement officials had already discovered material on Cruz’s social media accounts that was “very, very disturbing.”
Jim Gard, a math teacher at the school, said Cruz was in his class in 2016 and appeared to be a “quiet” student. But Gard also recalled that “there was concern” about his behavior on the part of the school administration, which emailed teachers relaying those fears.
The massacre called to mind other mass shootings at U.S. schools, including one at Sandy Hook Elementary School in Newtown, Connecticut, in 2012, in which 20 students and 6 adults were killed.
More than 40 “active shooter” episodes in schools have been recorded in the U.S. since 2000, according to FBI and news reports. Two 15-year-old students were killed and 18 more people were injured last month in a school in rural Benton, Kentucky. The shootings have become common enough that many schools, including Stoneman Douglas High, run annual drills in which students practice huddling in classrooms behind locked doors.