The 19-year-old is being held on 17 counts of premeditated murder. (Photo / Broward County Jail)

There was plenty to be alarmed about.

Math teacher Jim Gard, who taught Cruz last year before he was expelled from Stoneman Douglas, said that at some point during that period, the school administration sent out a note with a vague suggestion of concern, asking teachers to keep an eye on Cruz. "I don't recall the exact message," Gard said, "but it was an email notice they sent out."

"We were told last year that he wasn't allowed on campus with a backpack on him," Gard told the Miami Herald. "There were problems with him last year threatening students, and I guess he was asked to leave campus."

And Broward County Mayor Beam Furr told CNN that Cruz had been getting treatment at a mental health clinic for a while, but that he had not been back to the clinic for more than a year. "It wasn't like there wasn't concern for him," Furr told CNN. "We try to keep our eyes out on those kids who aren't connected. . . . In this case we didn't find a way to connect with this kid."

Now it's emerged Cruz was a member of a white nationalist group and participated in paramilitary drills in Tallahassee.

Jordan Jereb told the Associated Press that his group wants Florida to become a white ethno-state. He said his group holds "spontaneous random demonstrations" and tries not to participate in the modern world.

Jereb said he didn't know Cruz personally and that "he acted on his own behalf of what he just did and he's solely responsible for what he just did".

He also said Cruz had "trouble with a girl" and he believed the timing of the attack, on Valentine's Day, wasn't a coincidence.

Cruz's social media account was filled with pictures of him posing with weapons.

Cruz apparently fell off the radar. But he was having a rough time.

His adoptive 68-year-old mother, Lynda Cruz, had died in November of pneumonia. With her death, Cruz lost one of only relatives he had left in the world, said family and friends.

Lynda Cruz's sister-in-law, Barbara Kumbatovic said that his adoptive father Roger died of a heart attack several years ago, leaving Lynda to raise Cruz and his half brother, on her own.

"Lynda was very close to them," Kumbatovic told The Post. "She put a lot of time and effort into those boys, trying to give them a good life and upbringing."

One of the boys was the quiet one and seemed to stay out of trouble, but Nikolas, however, kept getting into problems at school, Kumbatovic said.

Neighbours told the Sun-Sentinel that police were called out repeatedly to deal with complaints about Nikolas. Shelby Speno said he was seen shooting at chickens owned by a resident. Malcolm Roxburgh, a neighbour of the Cruz family, told the Sun-Sentinel that Nikolas took a dislike to the pigs kept as pets by a family. "He sent over his dog . . . to try to attack them."

FBI acknowledges receiving shooting warning

"Lynda dealt with it like most parents did. She was probably too good to him," Kumbatovic said. "She was a lovely woman. She was a hard working woman. She made a beautiful home for them. She put a lot of effort and time into their schooling, their recreation, whatever they needed. She was a good parent. and she went over and above because she needed to compensate for being a single parent."

"I don't think it had anything to do with his upbringing. It could have been the loss of his mom. I don't know," she said.

After her death, Cruz and his half-brother stayed with friends in Lake Worth in Palm Beach County. Then he asked a former classmate from Stoneman Douglas High School if he could move in with him. Cruz's friend and his friend's parents agreed and opened up their home to him, said Jim Lewis, an attorney representing the family who took in Cruz. "It wasn't working out" in Lake Worth, said Lewis.

"The family brought him into their home," Lewis told The Post. "They got him a job at a local dollar store. They didn't see anything that would suggest any violence. He was depressed, maybe a little quirky. But they never saw anything violent. . . . He was just a little depressed and seemed to be working through it," Lewis said.

Years earlier and in recent months, however, young people acquainted with Cruz, like Mutchler, had seen enough to disturb them.

Cruz posing with hunting knives.

Joshua Charo, 16, a former classmate during their freshman year, told the Miami Herald that all Cruz would "talk about is guns, knives and hunting." While Charo said Cruz joined the Junior Reserve Officers' Training Corps as a freshman, he continued to be "into some weird stuff," like shooting rats with a BB gun.

Drew Fairchild, also a classmate during Cruz's freshman year, agreed. "He used to have weird, random outbursts," he told the Herald, "cursing at teachers. He was a troubled kid."

He was suspended from Stoneman Douglas for fighting, Charo told the Herald, and because was found with bullets in his backpack.

A classmate, Victoria Olvera, 17, told the Associated Press, that Cruz was expelled last school year after a fight with his ex-girlfriend's new boyfriend.

Officials would not comment on Cruz's school record for privacy reasons. Broward County Sheriff Scott J. Israel said at a news conference only that Cruz was ultimately expelled from Stoneman Douglas for "disciplinary reasons."

He had since enrolled in a program trying to obtain his GED [General Educational Development - similar to high school diploma], Lewis said.

According to Lewis, Cruz already owned the AR-15 when he moved in with the family of his friend. Lewis said he was told that Cruz had bought it legally, something officials have yet to publicly confirm or deny. "It was his gun. He had brought it to the house when he moved in. It was secured in a gun cabinet in the house, but he had the key to it. I believe it was secured in his room," Lewis said. The family had not seen Cruz shooting the AR-15 since he moved in with him.

Cruz's arsenal of weapons, as shown on his Instagram account.

Mackenzie Hill, a 17-year-old junior at Stoneman Douglas, told The Post she has known Cruz since middle school, when he was always getting in trouble. More recently, she remembered seeing him at the dollar store where he worked.

"He would talk to me like he knew me, and it creeped me out," Hill said.

"I always had a bad feeling about him," she said. Hill, like others, also cited Instagram posts, which, in the wake of the killings, Israel called "very, very disturbing."

An Instagram account that appeared to belong to the suspect showed several photos of guns. And one appeared to show a gun's holographic laser sight pointed at a neighbourhood street. A second showed at least six rifles and handguns laid out on a bed with the caption "arsenal." Other pictures showed a box of large-calibre rounds with the caption "cost me $30." One of the most disturbing appeared to show a dead frog's bloodied corpse. Most of the photos were posted July 2017.

Just the day before the shooting, Cruz had gone to work his job at the dollar store, said Lewis. On most days the father of the family he was staying with dropped Cruz off at school. But on Wednesday, Cruz told the family something to the effect of "I don't go to school on Valentines day," Lewis said.

From sources - picture of #stonemanshooting suspect Nikolas Cruz taken into custody @WPTV @MerrisBadcock reporting on air pic.twitter.com/J301qFROdj

— Jennifer Tintner (@JenniferTintner) February 15, 2018

Authorities found and arrested Cruz not far from the house where he lived Wednesday afternoon following a manhunt that transfixed the region and spread panic through many nearby schools.

Michael Nembhard, a retiree who lives in Coral Springs, said he witnessed police arrest Cruz just outside his house near the corner of Wyndham Lake Blvd and Coral Ridge Drive.

A little while after 3pm, Nembhard was sitting in his garage watching the TV news with his garage door open when he heard an officer yell, "Get on the ground!"

When he looked up he saw a teenager lying on the ground, wearing a burgundy hoodie and dark pants. "The cop had his gun drawn and pointed at him" Nembhard said.

In phone interview, Nembhard said he believes Cruz had been walking on foot when he was arrested, because at first Nembhard saw only the one police officer and his police cruiser alongside the suspect on the ground with no other vehicles in sight. Within minutes, however, a swarm of officers and cruisers had descended on the quiet neighbourhood.

From about 150 feet away, Nembhard watched as authorities handcuffed Cruz and put him into a police cruiser. A few minutes later, authorities took him out and into an ambulance.