This was third school shooting incident in six months.
Tip: 銃乱射 means “random act of shooting”. If a shooter had a particular target, you cannot say 乱射 because 乱れる (pron. = みだれる) means “being disordered”… 乱射 also means that the act attributed to more than one casualties.
You should say 銃発砲事件 (じゅうはっぽうじけん) or 銃撃事件 (じゅうげきじけん )instead of 銃乱射事件 if a shooter aimed at a particular target.