BEND, Ore. (Diya TV) — The shotgun used in the Oct. 15 shooting at Silver Rail Elementary School was a birthday gift from the suspect’s mother, CBS News reported Monday, citing sources familiar with the investigation. The 16-year-old, Griffin J. John II, allegedly used it to kill three children and a teacher and wound two others.

CBS reported that Shauntai Nickerson bought the Maverick 88 pump-action 12-gauge shotgun in August and gave it to her son for recreational use. A law enforcement official separately told the Associated Press that Nickerson bought the gun. Police have not publicly confirmed how it came into the teenager’s possession.

The weapon’s path to the teenager is now a focus of a separate investigation by the parents of five-year-old victim Rhoam Summer, who hired attorneys to examine both the gun purchase and the school’s safety protocols. Their attorney said they have not determined whether Nickerson qualified to buy the firearm or whether the dealer knew it was intended for a minor.

Oregon law allows a minor to possess a shotgun provided by a parent or with a parent’s consent. That provision does not resolve questions about the purchase or transfer in this case, which remain under review. Nickerson has not publicly addressed CBS’s report that she gave her son the gun as a gift.

Police say the teen first fired at a passing pickup truck, then shot through glass panels in the school’s locked entrance and entered a classroom. The victims who died were children ages 5, 8 and 11, and 25-year-old teacher Megan Lambert. A seven-year-old girl and a 54-year-old teacher were wounded.

A teacher fought the gunman, and Kaylub Giamanco, a 36-year-old father of two Silver Rail students, followed him inside and shot him, police said. The suspect had previously attended the school but was not enrolled in the district. Investigators have not announced a motive and are reviewing his phone, computer and online activity.

The school district says it had security cameras, locked doors and fencing, and held lockdown drills twice a year. It has pledged to review its safety measures.