During the interrogation, Cruz revealed that he "entered the school campus armed with an AR-15 and began shooting students that he saw in the hallway and on the school grounds," according to CNN.
"Cruz stated that he brought additional loaded magazines to the school campus and kept them hidden in a backpack until he got on campus to begin his assault," a probable cause report on the attack stated.
Cruz's attorney told local media that he is on a suicide watch.
Public defender Gordon Weekes called his 19-year-old client a "deeply disturbed, emotionally broken" young man who has struggled with significant mental illness and trauma his entire life.
"He's gone through a lot in a very short period of time and that does not minimize the loss of those families, but we have to put that into the proper light," CNN quoted Weekes as saying.
Cruz was booked on 17 counts of premeditated murder on Thursday.
According to local media, 15 people were injured.
Further, the leader of a white supremacist group on Thursday reportedly claimed that Cruz was a member of his group and also participated in paramilitary drills in Tallahassee, according to reports. (ANI)