BROWARD COUNTY, Fla. (AP) –  A law enforcement official is telling The Associated Press that a former student accused of killing 17 people at a Broward County school on Wednesday afternoon legally purchased his AR-15 rifle about a year ago.

The official is familiar with the investigation into the school shooting but not authorized to discuss it publicly and spoke on condition of anonymity. Federal law allows people 18 and over to legally purchase long guns. At 21, people can legally buy handguns from a licensed dealer.

Nikolas Cruz, 19, was arrested on 17 counts of premeditated murder and booked into the Broward County Jail on Thursday morning.

Cruz is a troubled teenager who posted disturbing material on social media before the shooting spree, according to a law enforcement official and former schoolmates.

Detectives say Cruz was equipped with a gas mask, smoke grenades and multiple magazines of ammunition, when he opened fire with a semi-automatic weapon, killing 17 people and sending hundreds of students fleeing into the streets. It was the nation’s deadliest school shooting since a gunman attacked an elementary school in Newtown, Connecticut, more than five years ago.

Broward County Sheriff Scott Israel said Cruz had been expelled from Marjory Stoneman Douglas High School for “disciplinary reasons.” “I don’t know the specifics,” the sheriff said.

Math teacher Jim Gard told the Miami Herald that before Wednesday’s fatal shooting of 17 people, Cruz may have been identified as a potential threat – Gard believes the school had sent out an email warning teachers that Cruz shouldn’t be allowed on campus with a backpack.

“There were problems with him last year threatening students, and I guess he was asked to leave campus,” Gard told the paper.

Victoria Olvera, a 17-year-old junior, said Cruz was expelled last school year after a fight with his ex-girlfriend’s new boyfriend. She said Cruz had been abusive to his girlfriend.

School officials said Cruz was attending another school in Broward County after his expulsion. 

Cruz’s mother Lynda Cruz died of pneumonia on Nov. 1 neighbors, friends and family members said, according to the Sun Sentinel. Cruz and her husband, who died of a heart attack several years ago, adopted Nikolas and his biological brother, Zachary, after the couple moved from Long Island in New York to Broward County.

The boys were left in the care of a family friend after their mother died, family member Barbara Kumbatovich, of Long Island, said.

Unhappy there, Nikolas Cruz asked to move in with a friend’s family in northwest Broward. The family agreed and Cruz moved in around Thanksgiving. According to the family’s lawyer, who did not identify them, they knew that Cruz owned the AR-15 but made him keep it locked up in a cabinet. He did have the key, however.

Jim Lewis said the family is devastated and didn’t see this coming. They are cooperating with authorities, he said.

Longtime Cruz family neighbors Malcolm and Christine Roxburgh told the Sun Sentinel that the police came to the boy’s house many times, as he used to get in trouble and harass people. Malcolm Roxburgh said a neighbor across the street kept pigs, and Nicolas Cruz targeted the family.

“He didn’t like the pigs and didn’t like the neighbors, so he sent over his dog over there to try to attack them,” Roxburgh said.

His wife said she once caught Nikolas peeking in her window.

“I said, ‘What are you doing here?’ He said he was looking for golf balls. I said, ‘This isn’t the golf course,’” she said.

And, the couple said, when the boy didn’t want to go to school, he would bang his head against a cement wall. They were scared of him. “He could have killed any of us,” Christine Roxburgh said.

Broward County Mayor Beam Furr said during an interview with CNN that the shooter was getting treatment at a mental health clinic for a while, but that he hadn’t been back to the clinic for more than a year.

“It wasn’t like there wasn’t concern for him,” Furr said.

“We try to keep our eyes out on those kids who aren’t connected … Most teachers try to steer them toward some kind of connections. … In this case, we didn’t find a way to connect with this kid,” Furr said.

Israel said investigators were dissecting the suspect’s social media posts.

An official GoFundMe campaign has been created by the Broward Education Foundation. The funds raised will be used to provide direct relief and financial support to the victims and families following the shooting in Florida.RELATED COVERAGE-

“And some of the things that have come to mind are very, very disturbing,” he added without elaborating.

Daniel Huerfano, a student who fled Wednesday’s attack, said he recognized Cruz from an Instagram photo in which Cruz posed with a gun in front of his face. Huerfano recalled Cruz as a shy student and remembered seeing him walking around with his lunch bag.

“He was that weird kid that you see … like a loner,” he added.

Dakota Mutchler, a 17-year-old junior, said he used to be close friends with Cruz but hadn’t seen him in more than a year following his expulsion from school.

“He started progressively getting a little more weird,” Mutchler said.

Mutchler recalled Cruz posting on Instagram about killing animals and said he had talked about doing target practice in his backyard with a pellet gun.

“He started going after one of my friends, threatening her, and I cut him off from there,” Mutchler said.

“I think everyone had in their minds if anybody was going to do it, it was going to be him,” Mutchler said.

Broward County School District Superintendent Robert Runcie told reporters on Wednesday afternoon that he did not know of any threats posed by Cruz to the school.

“Typically you see in these situations that there potentially could have been signs out there,” Runcie said. “I would be speculating at this point if there were, but we didn’t have any warnings. There weren’t any phone calls or threats that we know of that were made.”

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