Oregon school shooter John Griffin identified as armed civilian Kaylub Giamanco stopped the rampage before police arrived, amid new details on how he forced his way in

An armed civilian, Kaylub Giamanco, 36, shot and killed 16-year-old John J. Griffin II before police arrived at Silver Rail Elementary School in Bend, Oregon, as fresh details emerge about the extreme measures the teen took to breach the building and why he targeted his former special-needs classroom. Griffin opened fire on a red pickup truck outside the school, tossed his mother's shotgun over the fence and climbed over to retrieve it, and — after bystanders blocked the front entrance — circled to the rear, shot through a safety lock, and burst inside, killing kindergartner Rhoam Summer, 5, an 8-year-old, an 11-year-old, and a teacher. The gun — a Maverick 88, 12-gauge pump-action shotgun — was legally purchased by his mother, Shauntai May Nickerson, around the time of his August birthday.

Nickerson, sobbing on her apartment porch, said: 'He was a good boy, he really was — if I could have prevented this, I would have.'

Giamanco, a father of two girls at the school, spotted Griffin while driving home for lunch, followed him inside, and fired; he holds a concealed carry permit and knows the family of a 7-year-old shot in the face who remains critically ill.

Democrats' push for tighter gun controls ran into the fact that it was an armed civilian, not police, who ended the rampage — reigniting the debate over gun-free zones.