A teen accused of gunning down three children and a teacher at an Oregon elementary school on Thursday has been identified as John J. Griffin II, three senior law enforcement sources briefed on the investigation told Jattvibe News.It was not immediately clear if the 16-year-old alleged gunman had a connection to Silver Rail Elementary School in Bend, where officials said an armed bystander fatally shot the teen and interrupted the shooting spree.Two senior law enforcement officials told Jattvibe News that the teen’s mother purchased the long gun he used around his birthday in August. Victims included children ages 5, 8 and 11. A 7-year-old and a teacher were critically injured. Follow live updates hereA makeshift memorial at Silver Rail Elementary School in Bend, Ore., on Friday.Haven Daley / APPolice and federal investigators have not publicly identified a motive. Officials said the gunman shot through a locked door to gain entry into the school around 1 p.m. local time.“There are simply no words for the loss that we have suffered today,” Bend Mayor Melanie Kebler said at a community vigil hours after the tragedy.