“Some time before 9:30 a.m. EST on Friday, December 14, 2012, Lanza shot and killed his mother Nancy Lanza, aged 52, with a .22-caliber Savage Mark II rifle at their Newtown home.”
“Shortly after 9:35 a.m., armed with his mother’s Bushmaster XM15-E2S rifle and ten magazines with 30 rounds each, Lanza shot his way through a glass panel next to the locked front entrance doors of the school.”
https://en.wikipedia.org/wiki/Sandy_Hook_Elementary_School_shooting
The gun at issue wasn’t sold to the killer.
You make an excellent point, and I have argued for years that Lanza committed murder to get his hands on that gun. But facts don’t matter anymore.