He has been charged with 17 counts of murder after Wednesday’s shooting at Marjory Stoneman Douglas High School in Parkland.
Wearing an orange jumpsuit with his hands and ankles both cuffed, 19-year-old Cruz kept his eyes facing the floor.
An official from the public defender’s office described Cruz as a “deeply troubled child who has endured a lot of emotional trauma in a short period of time.”
Cruz’s court-appointed lawyer said he had expressed remorse for his crimes.
Public defender Melisa McNeill told reporters: “He’s a broken human being. He’s sad, he’s mournful, he’s remorseful.”
A report from the Broward Sheriff’s Office: “Cruz stated that he was the gunman who entered the school campus armed with a AR-15 and began shooting students that he saw in the hallways and on the school grounds.
“Cruz stated that he brought additional loaded magazines to the school and kept them hidden in a backpack until he got on campus to begin his assault.”
Earlier today it was claimed Cruz was a member of a white nationalist group.
The leader of a white nationalist militia says Cruz was a member of his group and took part in paramilitary drills.
Republic of Florida leader Jordan Jereb said Cruz was involved within a cell of the organisation.
Mr Jereb said: “He had some involvement with the Clearwater Republic of Florida cell at some point.”
He said Cruz had some “trouble with a girl”, claiming the Valentine’s Day date of the attack was not a coincidence.
The shooting just north of Miami was the 18th in a US school this year, according to gun control group Everytown for Gun Safety, continuing a troubling pattern that has played out over the past few years.