(CNN) For years before Nikolas Cruz gunned down classmates and teachers at his former high school, his mother had repeatedly called police to the home to help deal with his violent outbursts, threats and self-destructive behavior, according to police documents obtained by CNN on Friday.

The incident reports, which are as recent as September 2016, describe Cruz as suffering from mental illness and being "emotionally handicapped," and being on behavioral medication. One notes, "He has mentioned in the past that he would like to purchase a firearm."

The documents include more than 30 reports going back as far as 2011, covering misbehavior by Cruz and some by his younger brother. They add further depth to the emerging portrait of Cruz as an unstable teen who had long been on the radar of law enforcement, behavioral specialists, teachers and fellow students.

Yet Cruz was still able to pass the nation's gun background check system in February 2017 and obtain an AR-15-style semiautomatic rifle, one that he used to kill 17 at Marjory Stoneman Douglas High School on Valentine's Day.

Police records about emergency calls to his home describe fights at home -- and a mother's concern about a son out of her control even as an adolescent.

The emergency calls that the police received from the home included incidents categorized as "mentally ill person," "child/elderly abuse," "domestic disturbance" and "missing person." At least two calls reported Cruz as missing, in 2012 and 2013.

The day before one of those incidents, in November 2012, Cruz's mother Lynda called to report that he had hit her with the plastic hose of a vacuum cleaner.

The young man's father, Roger P. Cruz, purchased the home in 1996 and the family lived there until they sold the home in early 2017, county property records show. Roger Cruz died in 2004, and Lynda died in November.

The vast majority of the police calls resulted in "no paperwork filed," according to a list obtained by CNN on Thursday. But the few that are described in police reports detail Cruz's multiple outbursts.

Lynda Cruz called police to their home on January 15, 2013, records show. According to a police report, she said 14-year-old Nikolas had refused to go to school that day, so she took away his Xbox "privileges" and stashed the computer game system in her vehicle. That enraged her teen, who "retaliated and threw a chair, dog bowl and a drinking glass across the room." The boy called his mother "a useless bitch" and other profanities she wouldn't share with police, she said.

The mother told police her son had a "history of developmental and learning disabilities," was "increasingly irate" and suffered from ADHD.

Police placed the teen in handcuffs and sat him in the back of the police car as cops interviewed his mom. Nina Barela, a counselor from the nearby Henderson Behavioral Health facility, where Cruz was a client for years, arrived at the home and "gave Nikolas his prescribed medication." The boy soon "began to calm down and cooperated."

Based on that fact and that he "did not make any threats of harm to him or others," the report said, Barela advised that it was unnecessary to invoke a Florida law allowing police to put a mentally ill person in custody.

"A Baker Act was not needed," the report said.

Florida school shooting suspect Nikolas Cruz at his arrest Wednesday.

Broward County Sheriff's deputies were called to the Parkland, Florida, home four days after Cruz's 18th birthday. He had lashed out at his mother over a disagreement about the paperwork he needed to get a Florida State identification card. Lynda Cruz was worried, she told police. Back when he was too young to legally buy a rifle, her son had mentioned he wanted to buy a gun. Now he was "cutting his arms ... to get attention," she told them, according to one police report dated September 28, 2016.

The responding officer wrote that Cruz's therapist from Henderson, Jared Bienenfeld, was "on the scene at the home and deemed Nikolas to be no threat to anyone or himself at this present time."

An investigator with the Florida Department of Children and Families, Beatrice Thomas, was also there to check on the teen's well-being.

These reports add pivotal details to accounts by neighbors, who told CNN that Cruz grew up in a home that received frequent visits from law enforcement.

A former schoolmate, Brody Speno, said he knew Cruz since elementary school. He described him as "an evil kid" who was "always getting in trouble."

He recalled Cruz stealing people's mail, throwing rocks at cars and tormenting animals. He described one incident in which he said Cruz "cornered a squirrel and was trying to throw rocks at it and kill it."

Cruz was eventually expelled for disciplinary reasons from Marjory Stoneman Douglas High, where he would later return to commit this week's massacre.

Sunrise Tactical, the gun store in Coral Springs, Florida, that sold a gun to Nikolas Cruz.

In early 2017, Cruz bought an AR-15-style rifle from a small nearby gun store, Sunrise Tactical Supply in Coral Springs. Officials say he passed the required government background check, and bought it legally.

Thursday evening, a lawyer for the gun shop owner delivered this statement to news reporters:

"The Morrisons here sold a lawful weapon to someone who was mentally ill. Someone who fell through the cracks. Someone who was not held accountable for their actions when they were expelled from school. Someone who was not put into any sort of database and someone who was essentially allowed to go unchecked before walking into this store and purchasing a firearm," said Douglas Rudman, the attorney representing shop owner Michael F. Morrison.

The nation's gun-buying background check system is supposed to keep firearms out of reach for dangerous individuals. But it's not meant to catch early warning signs like those exhibited by Cruz.

The system checks for felony convictions, instances of domestic violence, addiction to illegal drugs and involuntary commitments due to mental illness.

But it does not check for school expulsions, other mental health history or domestic disturbances that do not result in criminal charges.

The system also does not review a person's public statements or explicit threats to commit violence, such as Cruz's multiple comments online -- in his own name -- in which he boldly declared his intentions.

"I wanna shoot people with my AR-15," said one.

"Im going to be a professional school shooter," said another.