The 16-year-old gunman who shot and killed three children and a 25-year-old teacher at Silver Rail Elementary School in Bend, Oregon, on Thursday has been identified as Griffin J. John II, Bend’s police chief announced at a news conference Friday. Authorities said he was shot and killed by a passerby at the school. The suspect was a former student at Silver Rail Elementary School, police said. The attacker used a shotgun purchased by his mother, law enforcement sources told CBS News. Bend Police Chief Mike Krantz said Friday that a 12-gauge Maverick 88 pump-action shotgun was located near the suspect, as well as a backpack. Krantz said three types of ammunition were used in the shooting: buckshot, buckshot and bullets. The suspect fired up to 15 rounds during the shootout, Krantz said Friday, and another 44 remaining rounds were located at the scene. No reason for the attack has been given. Bend-La Pine Schools Superintendent Steven Cook said at Friday’s news conference that the classroom where the shooting occurred was a special needs classroom, and revealed that the suspect had been a special needs student at that school. In 2020, the suspect’s mother, Shauntai Nickerson, spoke to a local television station about her then-10-year-old son, who she said had special needs and was struggling to learn from home during the pandemic. Krantz said the suspect approached the school fence on foot, threw the shotgun over the fence and then climbed over it himself. When he was confronted by a man passing by in a pickup truck, he fired at the truck, hitting it at least three times, Krantz said. That driver then continued driving and made the initial call to 911. It was at that point that the bystander who would later kill the suspect, a 36-year-old man whose children attend the school, witnessed the shooting and drove to the school parking lot. Krantz said the suspect forced his way into the school by firing several bullets into the glass panels of a set of double doors. He then went directly to the classroom immediately to the left of those doors, where he opened fire. “All of the victims were shot in that classroom,” Krantz said. Krantz told reporters Friday that the bystander, identified by his family as Kaylub Giamanco, removed a .40-caliber handgun he legally owned from his vehicle and entered the school and classroom where the shooting was taking place. “As he entered through the open doors, he heard gunshots and saw a teacher involved in a physical altercation with the suspect,” Krantz said. “He then went to the classroom where the struggle was occurring and fired his gun, striking the suspect several times.” Krantz also praised the “heroic actions” of the teacher who confronted the suspect in the physical struggle, saying she “threw her cell phone at the suspect and then knocked him down and struggled to get the firearm away from him.” That teacher, who was not injured, “almost certainly helped prevent further bloodshed,” Krantz said. Law enforcement sources told CBS News that investigators are reviewing his computer, phone, social media, search history and other online activities. They are investigating whether the shooter may have been obsessed with violence, including previous mass shootings. Sources emphasized that investigators are in the preliminary stages of their investigation. The children killed in the shooting were ages 5, 8 and 11, Krantz said. Police and his family identified the 5-year-old victim as Rhoam Summer. Bend police identified the slain 25-year-old teacher as Meghan Lambert. The families of the other two children have not released their names, Bend police said. Two other people, a 7-year-old girl and a 54-year-old teacher, were injured. The 7-year-old girl was being treated at Oregon Health and Science University in Portland, where she was in serious but stable condition, Krantz said Friday. The teacher, identified by her family to CBS News as Becky Drury, suffered serious but non-life-threatening injuries, Krantz said. She was being treated at St. Charles Medical Center. The family of Giamanco, a Bend resident with two daughters who attend Silver Rail Elementary School, issued a statement Friday saying Giamanco “is not seeking recognition, but rather wishes to express his gratitude to first responders, school staff and the community for the outpouring of love and support.” Police said they responded within minutes to 911 calls from the school and found the shooter deceased and other victims inside. Rhona Tarrant contributed to this report. More from CBS News Go deeper with The Free Press in: