SANTA CLARITA, Calif. (AP) -- The death of a 16-year-old boy who killed two students and wounded three others at his Southern California high school has left investigators struggling to discover what prompted the deadly attack.
Friends and neighbors described Nathaniel Tennosuke Berhow as bright, funny, quiet and above all normal before he pulled a gun from his backpack Thursday and in 16 seconds shot five students at random before saving the last bullet for himself.
Berhow died Friday afternoon from a self-inflicted gunshot wound to the head. His mother was present when he died, the Los Angeles County Sheriff's Department said in a statement.
Berhow had shown no signs of violence and didn't appear to be linked to any ideology or terrorist group, authorities said.
After more than 40 interviews and a search of his home, authorities still were in the dark, Capt. Kent Wegener of the Sheriff's Department's homicide unit said at a press conference.
"We did not find any manifesto, any diary that spelled it out, any suicide note or any writings," he said.
But if the teen's motivation was murky, his actions were planned and deliberate, Sheriff Alex Villanueva said.
Berhow's mother dropped him off at Saugus High School in the Los Angeles suburb of Santa Clarita Thursday morning, which was his birthday. He walked alone to the center of a school open-air quad. Security camera video showed him dropping his backpack and pulling out a .45-caliber handgun. He began firing, cleared the jammed weapon and kept shooting.
Berhow counted his rounds, Villanueva said, saving the last bullet for himself.
The dead were identified as 15-year-old Gracie Anne Muehlberger and 14-year-old Dominic Blackwell.
Bryan and Cindy Muehlberger said they shared the news of their daughter's death with "unexplainable brokenness." They described her as their "Cinderella, the daughter we always dreamed to have," and said her two brothers were heartbroken.
"She will never get to drive a car, fall in love, build a career, get married, have children and do all the other things everyone takes for granted in this short thing called life," they said in a statement.
"We miss her smile, laughter, sweet kisses, and her amazing sense of humor," the parents said.
Dominic Blackwell was a member of the Junior Reserve Officers' Training Corps.
"I've known him since I was five," student Joshua Mourthi told KABC-TV. "So, he used to be my neighbor. He could make anyone smile. You could be having the worst day and he'd walk up and say, 'Hey, how's your day going?' and you'd immediately start smiling."
Two girls, ages 14 and 15, were shot in the torso and should be released from the hospital over the weekend, doctors said Friday. A 14-year-old boy was treated and released.
Berhow was a Boy Scout and had previously run track for his school.
Friends said Berhow could be introverted but he had a girlfriend and a good social network focused on his cross-country teammates.
Berhow's father was an avid hunter who died two years ago. Police said they found several firearms at Berhow's home and some were unregistered. The semi-automatic handgun used by the boy also was unregistered. The Bureau of Alcohol, Tobacco, Firearms and Explosives was working with police to determine where Berhow got the handgun.
The common image of a mass shooter is "a loner, someone who is socially awkward, doesn't get along, some violent tendencies, dark brooding and online strange postings --- stuff like that," Villanueva said.
With this boy, investigators have found "nothing out of the ordinary. He's a cookie-cutter kid that you could find anywhere."
The stereotype of the loser sociopath is often inaccurate, according to the psychologist who co-wrote federal guidelines for assessing school shooting threats.
Marissa Randazzo, who has interviewed five shooters, said most of those she studied were academically successful and weren't social outcasts.
What pushes most shooters is some kind of loss or disappointment, often recent, followed by the inability to cope with a feeling of being overwhelmed, said Randazzo, a former chief research psychologist at the U.S. Secret Service who is now CEO of a threat-assessments firm.
"These are acts of suicide as much as homicide," she said.