Nikolas Cruz has pleaded guilty to all charges against him in the 2018 mass shooting he carried out at Marjorie Stoneman Douglas High School in Parkland, Florida.

Per BBC News, 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.

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He faces 34 counts, 17 of which are first-degree murder, carrying a minimum penalty of life in prison with no chance of parole and a maximum penalty of death, NBC News reports.

The other 17 counts are attempted murder in the first degree. Prosecutors can use each of the attempted murder charges and additional murder charges as aggravating factors at his sentencing hearing.

Fourteen of those who died were students, and three were members of staff.

Cruz killed his victims on Valentine's Day 2018 during a seven-minute rampage through a three-storey building at the school. Investigators said he shot victims in the hallways and in classrooms with an AR-15 semiautomatic rifle.

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Cruz had been expelled from the school back in 2017 after a history of threatening, frightening, unusual, and sometimes violent behavior that dated back to preschool.

In court on Wednesday, Judge Scherer asked Cruz how he pleaded to each murder. Following the plea, Cruz tearfully addressed the judge and the victims' families.

Per BBC News, he said: "I am very sorry for what I did and have to live with it every day. If I were to get a second chance, I would do everything in my power to help others."

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"I have to live with this every day and it brings me nightmares that I can’t live with myself sometimes but I try to push through," he added.

He also said that he believes that the US would "do better if everyone would stop smoking marijuana," per Reuters.

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 2022.

Featured image credit: Tribune Content Agency LLC / Alamy

Parkland school shooter Nikolas Cruz pleads guilty to 2018 murder of 17 classmates