Nikolas Cruz has pleaded guilty to the murders of 17 people killed in the 2018 high school massacre in Parkland, Florida.
The 23-year-old entered his pleas in a courtroom in front of a dozen relatives of victims after answering a long list of questions from Circuit Judge Elizabeth Scherer aimed at confirming his mental competency.
He was charged with 17 counts of murder and 17 counts of attempted first-degree murder for those wounded in the 14 February 2018 attack at Marjory Stoneman Douglas High School in Parkland, just outside Fort Lauderdale.
Cruz pleaded guilty on all counts.
Fourteen of those who died were students, and three were staff.
A penalty trial will now determine if Cruz will receive a sentence of death or life in prison without parole.
Judge Scherer plans to begin screening jurors next month in hopes testimony can begin in January.
Cruz’s attorneys announced his intention to plead guilty at a hearing last week.
Fred Guttenberg, whose 14-year-old daughter Jaime died in the shooting, said he had visited her grave this week to ask her for the strength to get through Wednesday’s hearing.
“She was the toughest, wisest person I ever knew,” he said.
“My daughter always fought for what was right. My daughter despised bullies and would put herself in the middle of someone being bullied to make it stop.”
Cruz killed his victims on Valentine’s Day 2018 during a seven-minute rampage through a three-storey building at Stoneman Douglas.
Investigators said he shot victims in the hallways and in classrooms with an AR-15 semiautomatic rifle.
Cruz had been expelled from Stoneman Douglas in 2017 after a history of threatening, frightening, unusual and sometimes violent behaviour that dated back to preschool.
The shootings caused some Stoneman Douglas students to launch the March for Our Lives movement, which pushes for stronger gun restrictions in the US.
Since days after the shooting, Cruz’s attorneys had offered to have him plead guilty in exchange for a life sentence, saying that would spare the community the turmoil of reliving the attack at trial.
But longstanding Broward State Attorney Mike Satz rejected the offer, saying Cruz deserved a death sentence, and appointed himself lead prosecutor.
Satz, 79, stepped down as state attorney in January after 44 years, but remains Cruz’s chief prosecutor.
His successor, Harold Pryor, opposes the death penalty but has said he will follow the law.
Like Satz, he never accepted the defence offer. Doing so as an elected official would have been difficult, even in liberal Broward County, where Democrats outnumber Republicans by more than two to one.
Given Cruz’s guilty plea, his attorneys will be able to argue during the penalty hearing that he took responsibility for his actions.