I saw somewhere that the shooter is 19 years old, and a former student of the school.
I don't know how to reconcile reports that the shooter was tackled by a teacher, who was seriously wounded, with other reports that the shooter was shot by an SRO. Does that mean there were two (at least) people involved in stopping the shooter, or was the SRO referred to as a "teacher"? We'll have to wait for details to filter out.