Commentary As has been the case with so many other school shootings over several years, last week’s murder spree at Oakland High School in suburban Detroit might have been avoided if actions had been taken in the face of several obvious warning signs. Ethan Crumbley, 15, is charged with murdering four of his fellow students and wounding with intent to kill seven others. He has also been charged with terrorism. There were a series of signs leading up to this tragedy—as there usually are—that should have alerted people that Crumbley was a serious threat. He had displayed disciplinary problems for some time. On the day of the shooting, he was summoned to the school office after misbehaving. His parents were also called in, an indication that officials were taking this latest incident more seriously than previous ones. Oakland prosecutor Karen McDonald told CNN there is a “strong possibility” Crumbley had the gun …