Nikolas Cruz, who is accused of murdering 17 people in Wednesday’s Florida high school shooting, lived with two different families since his mother's death in November, had been expelled from the school he allegedly attacked and reportedly killed chickens and frogs -- sometimes posting the gruesome pictures of the dead animals on social media.

Cruz, who was adopted at birth along with his biological brother, appeared to have a tough time after his mother died a few months ago due to pneumonia, the South Florida Sun-Sentinel reported. Cruz's father died when he was younger.

The 19-year-old man, who was described as “weird” and a “loner,” was expelled from the same school he allegedly opened fire on Wednesday. The Sun-Sentinel reported Cruz was expelled for “disciplinary problems.”

Nikolas Cruz was charged with 17 counts of premeditated murder.  (Instagram)

"I think everyone had in their minds if anybody was going to do it, it was going to be him," said Victoria Olvera, a 17-year-old junior at the school.

Olvera said Cruz was expelled last school year because he got into a fight with his ex-girlfriend's new boyfriend. She said he had been abusive to his girlfriend.

"I think everyone had in their minds if anybody was going to do it, it was going to be him."

- Victoria Olvera

The leader of a white nationalist militia said Cruz was a member of his group and participated in paramilitary drills in Tallahassee. Jordan Jereb of the Republic of Florida told The Associated Press he knew 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." It was not immediately clear if Jereb's claims could be verified. 

Police said Cruz used an AR-15 and had multiple magazines on him during the shooting. Cruz’s attorney Jim Lewis said the firearm was legally purchased.

Cruz and his brother were left in the care of a family friend after their mother died in November, but he was reportedly unhappy at the new location and asked to move in with a friend’s family in northwest Broward.

The teen moved in with that family after his mother’s Nov. 1 death and was allowed to keep the AR-15 as long as it was locked in a safe, Lewis said.

GUNMAN WHO KILLED 17 RAN OUT OF HS WITH PANICKED STUDENTS, COPS SAY

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Nikolas Cruz was described by classmates as "weird" and a "loner."

“It was his gun,” Lewis said. “The family made him keep it in a locked gun cabinet in the house, but he had a key.”

The family said they never witnessed Lewis shooting the gun, but did see him with pellet guns.

Barbara Kumbatovich, the sister of Cruz’s mother, Lynda, said she heard the news at her home in Long Island, N.Y., and could not believe she knew the suspect. She told the South Florida Sun-Sentinel she only met Cruz once at a funeral when he was young.

A picture on Nikolas Cruz's Instagram page shows him holding a rifle.  (Instagram)

“I know she had been having some issues with them, especially the older one. He was being a problem. I know he did have some issues and he may have been taking medication. [He] did have some kind of emotional or difficulties,” Kumbatovich said. “[Lynda] kept a really close handle on both boys. They were not major issues, as far as I know, just things teenagers do, like not coming home on time, maybe being disrespectful.”

Kumbatovich told The Washington Post her sister was close with the boys who "put a lot of time and effort into those boys, trying to give them a good life and upbringing." 

She said she does not believe Cruz allegedly opened fire at the school due to his upbringing but maybe because of the recent passing of his mother. 

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

After he moved in with the family friend in Palm Beach County, he was urged to get a job and attend adult education classes.

Janine Kartiganer, a former neighbor of Cruz, said the teen looked “very troubled.”

“He wore a hoodie and always had his head down,” she said. “He looked depressed.”

Emily Sucher, a junior at the high school, said she remembered Cruz as “an off kid” who “would smile weirdly, make weird comments.”

Another student, Trevor Hart, said Cruz “seemed like he really didn’t like school.” He also said the teen, who was enrolled in the Army ROTC at the school, had “a bunch of weapons” and often spoke about killing small animals.

Joshua Charo, 16, told The Washington Post that Cruz spoke about "guns, knives and hunting" often and "was into some weird stuff, such as shooting rats with a BB gun."

Charo said Cruz was suspended from the school for fighting and having bullets discovered in his backpack.

Drew Fairchild, another classmate, called Cruz "a troubled kid" who cursed at teachers often. 

Mike Watford, who graduated from the high school in 2016, told BuzzFeed News that "something definitely pushed [the suspect]" before Wednesday's shooting.

Pictures from Nikolas Cruz's Instagram page show his fascination for guns.  (Instagram)

Cruz often said "how tired he was of everyone picking on him and the staff doing nothing about it," Watford said.

A math teacher, Jim Gard, said Cruz was infatuated with a female student at the school “to the point of stalking her.” Gard also said he believed the school had sent out an email warning teachers that Cruz shouldn’t be allowed on school grounds with a backpack.

FLORIDA HIGH SCHOOL FOOTBALL COACH WHO WAS SEEN SHIELDING STUDENTS FROM GUNFIRE DIES

Officials did not immediately say why Cruz was expelled from the high school.

Police escort Nikolas Cruz into Broward County Jail following a shooting incident at Marjory Stoneman Douglas High School, in Fort Lauderdale, Florida, U.S. February 15, 2018 in a still image from video. WSVN.com via REUTERS. ATTENTION EDITORS - THIS IMAGES HAS BEEN PROVIDED BY A THIRD PARTY. NO RESALES, NO ARCHIVES. MANDATORY CREDIT. NO ACCESS SOUTHEAST FLORIDA MEDIA. - RC1625BF04C0

Nikolas Cruz was seen being booked after being held by police.  (Reuters)

Shelby Speno, a former neighbor, said Cruz would shoot at their neighbor’s chickens and threw eggs at her husband’s car. She said Cruz’s mother “had her hands full.”

“I told my husband I was so glad they moved. I’m afraid he was the kind of kid who would do something crazy,” Shelby said. “The older he gets, the worse kind of trouble he got into.”

Other neighbors said police were called to Cruz’s house multiple times and the teen attempted to steal a bike from a neighbor’s garage.

Stephanie Bell, the senior director of cruelty casework at PETA, told Fox News it was "no surprise" to the organization that Cruz was cruel to animals. 

"It is no surprise to PETA that before he allegedly massacred 17 people at a school in Parkland, Florida, Nikolas Cruz is said to have talked about shooting small animals, including lizards, squirrels, frogs, and a neighbor's chickens, and reportedly sent his dog to a neighbor's house to attack the pigs there. The FBI has identified cruelty to animals as a warning sign of more violence to come, and many school shooters and serial killers have a history of abusing animals. While the issues of gun control and mental health rage on, one simple way to prevent future acts of violence is for local law-enforcement officials to pursue the strongest penalties possible in cruelty-to-animals cases—for everyone's sake—and for those who hear about or witness animal abuse to report it," Bell said in a statement.

Authorities are looking into the suspect’s “disturbing” social media posts, which appeared to include Cruz posing with guns.

“And some of the things that have come to mind are very, very disturbing,” Broward County Sheriff Scott Israel said of the social media posts.

Israel said authorities have not determined a motive for the shooting.

Buzzfeed News reported a YouTube vlogger flagged a comment on one of his videos from a person named Nikolas Cruz that said: “I’m going to be a professional school shooter.” The vlogger, Ben Bennight, said he alerted the FBI to the comment last fall.

On Thursday, Cruz made his first court appearance after being charged with 17 counts of premeditated murder in the shooting at Marjory Stoneman Douglas High School. Cruz only said, "Yes, ma'am" and "Yes, your honor" during his brief court appearance. 

He was ordered held without bond.

The Associated Press contributed to this report.