|Kendal Sanders, age 13 (source)|
Campbell entered the school gym, where a large number of students were gathered before school started, and opened fire.
A good article with details and images.
He shot an 11-year old boy twice in the face, and shot a 13-year old girl, Kendal Sanders, in the right shoulder. Both are now in the hospital. The girl is in satisfactory condition, while the boy has had two surgeries and is in critical condition. The 11-year old believes he was the intended target.
|Shooter Mason Campbell, age 12, posing|
with a shot animal (source)
The school had a security guard, but the guard wasn't near the situation as it unfolded.
The entire shooting lasted about 10 seconds.
The shooter, Mason Campbell, is apparently a hunter (see image) and is therefore, presumably, familiar with gun and gun safety.
The gun reportedly came from the family home. How had it been stored?
Every gun in the hands of a child must first pass through the hands of an adult.