Commentary Children cannot legally buy guns. It’s adults who introduce guns into a home, where curious or disturbed kids can get access to the deadly weapons. So, who is to blame if a youngster gets a firearm and uses it to commit mass murder, as 15-year-old Ethan Crumbley did in Oxford, Michigan, recently? The law in Michigan says no one under 21 may legally buy or possess a handgun. The store clerk where James Crumbley, Ethan’s dad, bought the gun confirmed that the boy was there when the 9mm Sig Sauer SP pistol was purchased. A social media post from Ethan’s mom, Jennifer, showed her with Ethan at a gun range and the caption, “Mom and son day, testing out his new Christmas present.” The parents later admitted they kept the gun in an unlocked nightstand drawer. After a teacher discovered Ethan shopping for ammunition on his phone, she reportedly …