Broward County Sheriff(NEW YORK) — The Anti-Defamation League, a civil rights watchdog, told ABC News they have information they believe to be credible linking Nikolas Cruz, the Florida school shooting suspect, to a white supremacist group called Republic of Florida.

The ADL said ROF leader Jordan Jereb told them Cruz was associated with his group. Jereb, who is based in Tallahassee, said Cruz was brought into the group by another member and had participated in one or more ROF training exercises in the Tallahassee area, the ADL said. Law enforcement officials have not confirmed the link.

ROF has mostly young members in north and south Florida and describes itself as a “white civil rights organization fighting for white identitarian politics” and seeks to create a “white ethnostate” in Florida.

Three former schoolmates of Cruz told ABC News that Cruz was part of the group. They claimed he marched with the group frequently and was often seen with Jereb, who also confirmed to ABC News that Cruz was, at least at one point, part of that group.

Jereb told the ADL that ROF had not ordered Cruz to take any such action. He told ABC News he has not spoken to Cruz in “some time” but said “he knew he would getting this call.” He would not comment further but emphasized that his group was not a terrorist organization.

Authorities are still digging for clues to why Cruz allegedly opened fire outside Marjory Stoneman Douglas High School in Parkland, Florida, on Wednesday, killing 17 people.

Family members, classmates and former friends described Cruz, a 19-year-old former student, as a troubled teen who was largely alone in the world when he allegedly stormed through the school carrying an AR-15 rifle and multiple magazines.

He was able to leave the school after the shooting by blending in with other students who were trying to escape, but he was apprehended shortly thereafter. He has been answering questions from investigators working on the case.

Cruz was adopted as an infant, but he had been living with the family of a classmate after the sudden death of his adoptive mother late last year. His adoptive father died in 2005.

In an interview with ABC News’ George Stephanopoulos, an attorney for the family that had taken Cruz in for the past few months said Cruz was “depressed” following his mother’s death but he had been going to therapy.

The family is still “shocked,” he said, that Cruz would allegedly engage in mass violence.

“They indicated they saw nothing like this coming,” Lewis said. “They never saw any anger, no bad feelings about the school.”

They were aware that Cruz was in possession of a military-style assault weapon, he said, which two law enforcement officials tell ABC News was legally purchased by Cruz within the past year from a federally licensed dealer. They insisted that it be locked in a safe.

“He brought it into the home and it was in a locked gun safe,” Lewis said. “That was the condition when he came into their home that the gun was locked away.”

Cruz’s former classmates, however, were less surprised.

A student who told ABC News that he participated in Junior ROTC with Cruz described him as a “psycho.” Cruz was a well-known weapons enthusiast, the student said, who once tried to sell knives to a classmate.

Another student told ABC News that before Cruz was expelled from the school he was barred from carrying a backpack on campus. The classmate said the rule was put in place after the school found bullet casings in his bag after a fight with another student.

One student said Cruz even once threatened to “shoot up” the school.

“About a year ago I saw him upset in the morning,” student Brent Black told ABC News. “And I was like, ‘yo what’s wrong with you?’ And he was like ‘umm, don’t know.’ And I was like ‘what’s up with you?’ He’s like ‘I swear to God I’ll shoot up this school.’ And then I was like ‘watch what you’re saying around me,’ and then I just left him after that. He came up to me later on the day and apologized for what he said.”

On Thursday, the FBI issued a statement saying that it was alerted in 2017 to a threat on YouTube by someone who said “I am going to be a school shooter.”

“In September 2017, the FBI received information about a comment made on a YouTube channel. The comment said, “I’m going to be a professional school shooter.” No other information was included in the comment which would indicate a particular time, location, or the true identity of the person who posted the comment. The FBI conducted database reviews and other checks, but was unable to further identify the person who posted the comment.”

According to Broward County Sheriff Scott Israel, investigators have already found some “disturbing” content on social media that could have provided warning signs.

“We have already begun to dissect his websites and things on social media that he was on, and some of the things that have come to mind are very, very disturbing,” Israel said.

The photos posted on an Instagram account law enforcement sources tell ABC News belongs to the suspected shooter shows a young man displaying an arsenal of weapons.

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