Colt Gray is seen in a booking photo.

During a search of the home of Colt Gray, the suspect in the Apalachee High School shooting, authorities found documents they believe he had written relating to previous school shootings, a law enforcement source familiar with the investigation told CNN.

The source said the writings were discovered in Gray’s bedroom and contained references to the 2018 massacre at Marjory Stoneman Douglas High School in Florida.

The discovery, which could shed more light on the motive for the shooting, comes as an increasingly clear account of Gray’s turbulent family life in the years before the fatal attack emerges through a CNN review of court and police records, social media posts and an interview with his grandfather.

Gray’s parents have had a bitter separation and custody battle in recent years. They called the police on each other, the family was evicted from at least one home and Gray’s mother was arrested for scratching her husband’s car and possessing drugs, police records show.

At the same time, Gray’s mother and maternal grandfather have accused Gray’s father of verbally abusing his family for years. The grandfather, who wishes to remain anonymous, said he never saw any anger issues in the victim, but the turbulent family life affected the teenager.

To understand the suspected shooter’s motive, investigators are now examining his family’s previous contacts with the state’s child welfare agency, the director of the Georgia Bureau of Investigation said Wednesday.

Attempts to reach both of the suspect’s parents for comment on Wednesday and Thursday were unsuccessful.

Read the full investigation.