Parkland school shooter Nikolas Cruz to plead guilty to killing 17
Nikolas Cruz, accused of killing 17 in the February 14, 2018 massacre at a high school in Parkland Florida, pictured in court a day after the attack Susan. (STOCKER POOL/AFP/File)

The former student accused of the February 14, 2018 shooting rampage at a school in Parkland, Florida, will plead guilty to murdering 17 people, his lawyer told a court Friday.

Nikolas Cruz, who was 19 at the time, took a legally purchased AR-15 assault rifle into Marjory Stoneman Douglas High School, his former school, killing 17 students and staff members.

The Valentine's Day attack was the worst school massacre in the United States since the horror at Sandy Hook Elementary School in Newtown, Connecticut in 2012, which left 26 dead.

Now 23, Cruz was charged with 17 counts of premeditated murder and 17 counts of attempted murder for those he wounded in the attack.

"It is our intent to enter a change of plea as to both cases, to all charges," Cruz's attorney David Wheeler told a judge, indicating that Cruz would drop his initial innocent plea both for the murders and for physically attacking a jail officer after his arrest.

The shooting stunned the country and sparked new efforts, led by students from the school itself, for tougher gun controls -- although the polarized US Congress has yet to enact meaningful gun reform.

- Fixated by firearms -

Cruz bought the weapon legally, despite having been in local records as having a history of mental health problems.

Expelled from school for disciplinary reasons, Cruz was known to be fixated by firearms -- and had reportedly been identified as a potential threat to his classmates.

The FBI confirmed it was alerted several months earlier to a message posted on YouTube, in which a user named Nikolas Cruz vowed: "I'm going to be a professional school shooter."

On the day of the attack he arrived at the school in an Uber, quickly entered and began shooting, and left the scene nine minutes later, leaving behind a scene of carnage.

Footage recovered from his phone showed he had filmed his plans to attack his former school, saying his goal was to kill "at least 20 people."

He told a detective after his arrest he heard demons ordering him to "buy weapons, kill animals and destroy everything."

- Death penalty issue -

When he was arraigned on March 13, 2018, a "not guilty" plea was entered for Cruz as prosecutors said they would seek the death penalty.

Flowers and crosses hang on a fence in memory for the victims of the Marjory Stoneman Douglas High School shooting RHONA WISE AFP/File

At the time his lawyers let it be known that he would offer a guilty plea if the death penalty was taken off the table.

It was not clear Friday if any such deal had been reached.

In reaction to the news, Fred Guttenberg, whose 14-year-old daughter Jaime was killed in the attack, called on people to "remember the victims."

"Remember Jaime," he wrote on Twitter.

- Mentally competent -

Cruz appeared in a second court session Friday to enter his plea on the jail officer assault charges after state attorneys assured the Broward County circuit judge Elizabeth Scherer that he had been determined mentally competent.

Cruz appeared slight with short hair and wearing a Covid mask, and wore a blue pullover covering a white button-down shirt, tucked into khaki slacks.

"I'm alright," he said when Scherer asked how he was feeling.

"I don't believe I have any issues," he said to a question about his mental health.

Asked if he understood the four charges related to the assault, he answered yes, and confirmed he was pleading guilty to each.

Scherer said the assault charges could bring a minimum of 14 months and maximum of 26 years in prison if served consecutively, though noting he would get credit for the more than three years already spent in detention.

The court set a formal plea hearing on the murder charges for October 20.

After that the court would begin choosing jurors to debate the penalty, which could focus on the choice between execution or life in prison.