Authorities searching the home of the 14-year-old accused of killing four people at a Georgia high school this week found documents that they believe he wrote referencing past school shootings, a law enforcement source familiar with the investigation told CNN.

The source said that the writings were discovered in the bedroom of suspect Colt Gray, and included references to the 2018 massacre at Marjory Stoneman Douglas High School in Florida.

Live updates: The latest on the Georgia high school shooting

The discovery, which could shed more light on a motive for the shooting, comes amid an emerging portrait of Gray’s tumultuous family life in the years leading up to the deadly attack, revealed in a CNN review of court and law enforcement records, social media posts, and an interview with his grandfather.

As that portrait has emerged, so have details about the investigation and authorities’ pursuit of those they allege bear responsibility in the shooting. Gray told investigators, “I did it” while being questioned, Barrow County Sheriff Jud Smith told CNN on Thursday.

And while Gray faces four counts of felony murder, Gray’s father, Colin, also has been arrested in connection with the shooting, accused of “knowingly allowing his son … to possess a weapon,” Georgia Bureau of Investigation Director Chris Hosey said Thursday. Colin Gray was charged with four counts of involuntary manslaughter; two counts of second degree murder; and eight counts of cruelty to children, the GBI said.

As for Colt Gray’s family situation: His parents went through a bitter separation and custody dispute in recent years. They called law enforcement on each other, the family was evicted from at least one home, and Gray’s mother was arrested on suspicion of keying her husband’s car and drug possession, law enforcement records show.

At the same time, Gray’s mother and maternal grandfather have accused Gray’s father of being verbally abusive toward his family for years.

“He was just a good kid, but he lived in an environment that was hostile,” Charles Polhamus said of Colt Gray, his grandson, in an interview with CNN. “His dad beat up on him, I mean, I’m not talking about physical, but screaming and hollering, and he did the same thing to my daughter.”

The grandfather said he had never seen Colt Gray show any kind of anger problems, but that the turbulent family life had affected the teenager.

Now, investigators seeking to understand the suspect’s motive are looking into his family’s previous contacts with the state’s child protective services agency, the GBI director said Wednesday.

The suspect’s father told investigators this week he had purchased the gun used in the killings as a holiday present for his son in December 2023, according to two law enforcement sources with direct knowledge of the investigation. One source told CNN the AR-15-style rifle was purchased at a local gun store as a Christmas present. The other source described the gift as a holiday present.

Attempts to reach both of the suspect’s parents for comment on Wednesday and Thursday were unsuccessful. CNN was working to determine whether Colt Gray and Colin Gray have legal representation.

Colt Gray’s parents’ relationship started out with promise. In July 2011, shortly after he was born, his parents bought a small farm in Barrow County, Georgia, outside of the college town of Athens. They planned to “create a non-profit, therapeutic riding school for local, under-privileged children,” his mother, Marcee Gray, who worked in industrial engineering, later wrote in a LinkedIn post.

But those plans were derailed in part because her husband, Colin Gray, had at least three “major” back surgeries, she wrote. The couple, who had three children, later sold the farm in 2019, according to property records.

After they moved, the family faced lawsuits from multiple landlords, and were evicted from one home by a county sheriff’s deputy in July 2022 for failing to pay rent, according to court records. As part of the eviction, sheriff’s records show, deputies collected three firearms, including an AR-15, and at least one hunting bow, and kept them for safekeeping. The weapons were later “released to owner,” the documents say.

Later that year, Marcee Gray wrote on social media that she had left her husband.

“Finally separated from my abusive husband of almost 14yrs,” she wrote in one LinkedIn comment on a post from December 2022. “Hardest shit I’ve ever done but we’re in good hands.”

“I packed myself and my babies up and relocated to my hometown in south GA,” Gray added in another post in May 2023. “We are all good and my kids are thriving.”

School shooting threat investigated

The same month, however, law enforcement agents were investigating 13-year-old Colt Gray in connection with a school shooting threat. Investigators with the Jackson County Sheriff’s Office interviewed Colt and his father about a threat on the online chat platform Discord to commit a school shooting, documents obtained through a public records request show.

Colt Gray denied making the threat, an investigation report said. A Discord spokesperson told CNN on Wednesday that the platform removed an account “believed to be associated with” Gray in May 2023 for violating Discord’s policy against extremism.

Colin Gray told investigators he had hunting rifles in the house, and that “Colt is allowed to use them when supervised but does not have unfettered access to them,” the report said. The case was later cleared because the tip could not be substantiated.

Transcripts from the interview and a subsequent phone call show that Colin Gray said his son was “getting picked on at school,” with other students “pinching him and touching him… just ridiculed him day after day after day.” He also that that he was “trying to teach him about firearms and safety and how to do it all and get him… interested in the outdoors,” in part to get him away from video games.

“He knows the seriousness of weapons and what they can do and how to use them and not use them,” Colin Gray said.

In his interview, Colin Gray told investigators that he had separated from his wife, who took their two younger children with her. The suspect’s father said that Colt – the oldest of three siblings – had “had some problems” at a middle school in Jackson County but had since moved to another school and “it has gotten a lot better,” one of the investigators wrote.

Gray was only enrolled in the Jackson County school district between February and August 2022, said Edward Hooper, the spokesperson for the district. Jackson County is next to Barrow County, where Colt Gray is accused of killing two fellow students and two teachers at Apalachee High School.

In October 2023, Barrow County Sheriff’s deputies responded to a wellness check on the Gray family after Marcee Gray reported that she hadn’t heard from her husband or their children in two weeks. Colin Gray, who was at their residence, said all of their children were with him, a sheriff’s deputy wrote in a report.

Colin Gray gave the deputy a paper from the Georgia Division of Family and Children Services that showed “a safety plan was put in place for him to have the children with him” and Marcee Gray “could not see them without supervision,” the deputy wrote.

A spokesperson from the Georgia Department of Human Services said Thursday she could not comment on the case due to confidentiality laws. But Georgia Bureau of Investigation Director Chris Hosey said at a press conference Wednesday that the bureau was aware that the division had previously had “some previous contacts” with the Gray family, and “we are pursuing that avenue as well too to see if that has any connection with today’s incident.”

In November 2023, Colin Gray called law enforcement and accused his wife of keying a truck he drove for his work at a construction company, writing “abuse” and “liar” on it, according to a sheriff’s report.

Two days later, police arrested Marcee Gray at a Walmart in Winder due to an active warrant from another county. Police found methamphetamine, fentanyl, pain pills, and a glass pipe in her car, and she and another man who was in the vehicle were arrested, another sheriff’s report said.

After being arrested, Marcee Gray admitted keying her husband’s truck, saying she “lost it” after he refused to let her see her kids, the report said.

Marcee Gray pleaded guilty the following month to criminal damage to property, “criminal trespass - family violence,” and use of a license plate to conceal identity, and was sentenced to a total of five months’ probation after serving more than a month in custody. As part of her guilty plea, she was barred from contacting her husband except through a third party for divorce negotiations and custody discussions.

A friend of Marcee Gray, who asked not to be named for privacy, told CNN that the legal trouble she faced was “not the Marcee we know,” calling her a “sweet, caring, and smart woman” who had changed.

“Something happened in that relationship that went wrong,” the friend said.

According to Polhamus, Marcee Gray’s father, she lost custody of her children after failing a drug test, moved back in with her parents in south Georgia and is going through rehab.

Polhamus said he had never thought his grandson would be capable of such a deadly attack.

“I understand that Colt chose to do what he did, and I understand he has to pay for it,” he said. “But I’m telling you, the environment that he lived in… you put somebody in a situation like that for 10 or 11 years, guess what’s gonna happen? Nothing good.”

Discord account linked to suspect shared plans for mass shooting

The Discord account that the FBI had linked to Colt Gray last year referenced plans for a future mass shooting and shared screenshots of firearms, according to documents obtained by CNN.

“im committing a mass shooting and im waiting a good 2-3 years,” stated the account user, according to screenshots included in an FBI incident report from May 2023 obtained by CNN. “I cant kill myself yet, cause I’m not contributing anything to culture I need to go out knowing I did.”

The account referenced Adam Lanza, the Sandy Hook Elementary School shooter, and in separate posts shared a desire to target an elementary school and expressed frustration with the acceptance of transgender people.

Above a photograph of two firearms, the account posted, “I’m ready.”

The FBI tip was shared with the Jackson County Sheriff’s Office, which closed the investigation after finding that “the user behind the Discord account that made the threat cannot be substantiated.”

A Discord spokesperson told CNN on Wednesday the platform removed an account “believed to be associated with” Gray in May 2023 for violating Discord’s policy against extremism.

This story has been updated with additional reporting.

CNN’s Isabelle Chapman and Amanda Jackson contributed reporting.