Parent Mirna Herrera kneels with her daughters Liliana, 15, and Alexandra, 16 at the Central Park memorial for the Saugus High School victims in Santa Clarita, Calif., Friday, Nov. 15, 2019. Investigators said Friday they have yet to find a diary, manifesto or note that would explain why a boy killed two students outside his Southern California high school on his 16th birthday. (AP Photo/Damian Dovarganes)

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.

This undated photo provided by the Muehlberger family shows Gracie Anne Muehlberger, 15. She is one of two students who died when Nathaniel Tennosuke Berhow opened fire at Saugus High School in Santa Clarita, Calif., Thursday, Nov. 14, 2019. Berhow, 16, planned the attack at the Southern California high school, but investigators were so far unable to find out why he brought a gun to campus and opened fire, authorities said Friday. (Muehlberger family via AP)
Emily Boyle, a senior at Valencia High School brings flowers at a memorial near Saugus High School in Santa Clarita, Calif., Friday, Nov. 15, 2019. A homicide official says that investigators did not find a diary, manifesto or note belonging to the boy who killed two people outside his Southern California high school on his 16th birthday. Officials held a press conference Friday outside of the police station Santa Clarita. No motive or rationale has been established yet in the Thursday morning shooting at Saugus High School in the Los Angeles suburb of Santa Clarita. (AP Photo/Damian Dovarganes)
A Los Angeles Sheriff Sheriff's vehicle patrols the surroundings of the Saugus High School in Santa Clarita, Calif., Friday, Nov. 15, 2019. Investigators said Friday they have yet to find a diary, manifesto or note that would explain why a boy killed two students outside the Southern California high school on his 16th birthday. (AP Photo/Damian Dovarganes)
Deputy James Callahan, at podium, takes questions from the media at a news conference at the station Santa Clarita, Calif., Friday, Nov. 15, 2019. Callahan works as a school resource officer at Saugus High School, was on the scene in the aftermath of the shooting, (AP Photo/Damian Dovarganes)
Santa Clarita Mayor Marsha McLean, far left, Los Angeles Sheriff Sheriff Alex Villanueva, left, Detective Daniel Finn, at podium, and Deputy James Callahan, far right, take questions from the media at a news conference at the station Santa Clarita, Calif., Friday, Nov. 15, 2019. (AP Photo/Damian Dovarganes)
Doctors at Providence Holy Cross Hospital in Mission Hills tell reporters they treated a 15-year-old girl and a 14-year-old girl after Thursday's shooting at Saugus High School in Santa Clarita, during a news conference Friday, Nov. 15, 2019 in Los Angeles.  The suspected gunman shot five students, seemingly at random, and then shot himself in the head and remains in critical condition Friday.  (AP Photo/Damian Dovarganes)
Hannah Schooping-Gutierrez, center, a student at Saugus High School, is comforted by her boyfriend Declan Sheridan, at right, a student at nearby Valencia High School during a vigil at Central Park in the aftermath of a shooting at Saugus Thursday, Nov. 14, 2019, in Santa Clarita, Calif. (AP Photo/Marcio Jose Sanchez)
Students embrace during a vigil at Central Park in the aftermath of a shooting at Saugus High School Thursday, Nov. 14, 2019, in Santa Clarita, Calif. Los Angeles County sheriff’s officials say a 16-year-old student shot five classmates and then himself in a quad area of Saugus High School Thursday morning. (AP Photo/Marcio Jose Sanchez)
People hug each other during a vigil for the Saugus High School shooting victims at Central Park, Thursday, Nov. 14, 2019, in Santa Clarita, Calif. Los Angeles County sheriff’s officials say a 16-year-old student shot several classmates and then himself in a quad area of Saugus High School Thursday morning. (Hans Gutknecht/The Orange County Register/SCNG via AP)
Jessica Dumont, a former student at Saugus High School, places balloons on a makeshift memorial at Central Park in honor of the victims of a shooting at the high school Thursday, Nov. 14, 2019, in Santa Clarita, Calif. Los Angeles County sheriff’s officials say a 16-year-old student shot several classmates and then himself in a quad area of Saugus High School Thursday morning. (AP Photo/Marcio Jose Sanchez)
Members of Saugus High School's Air Force JUNIOR ROTC unit hold a moment of silence in memory of the victims of a shooting at the school earlier in the day Thursday, Nov. 14, 2019, in Santa Clarita, Calif. Los Angeles County sheriff’s officials say a 16-year-old student shot five classmates and then himself in a quad area of Saugus High School Thursday morning. (AP Photo/Marcio Jose Sanchez)
Flowers are placed in front of Saugus High School in the aftermath of a shooting on Thursday, Nov. 14, 2019, in Santa Clarita, Calif. (AP Photo/Marcio Jose Sanchez)
Ella Cabigting is embraced by her father Emerson as they reunite following a shooting at Saugus High School that injured several people, Thursday, Nov. 14, 2019, in Santa Clarita, Calif. (AP Photo/Ringo H.W. Chiu)
Emergency personnel remove an injured person following a shooting at Saugus High School, Thursday, Nov. 14, 2015 in Santa Clarita, Calif. (David Crane/The Orange County Register via AP)
Medical personnel load an injured person into an ambulance outside Saugus High School in Santa Clarita, Calif., after a student gunman opened fire at the school on Thursday, Nov. 14, 2015. (Rick McClure via AP)
Students are escorted out of Saugus High School after reports of a shooting on Thursday, Nov. 14, 2019, in Santa Clarita, Calif. (AP Photo/Marcio Jose Sanchez)
Student Sayla David, 12, holds thank you signs for first responders outside the Saugus High School in Santa Clarita, Calif., Friday, Nov. 15, 2019. A homicide official says that investigators did not find a diary, manifesto or note belonging to the boy who killed two people outside his Southern California high school on his 16th birthday. No motive or rationale has been established yet in the Thursday morning shooting at Saugus High School in the Los Angeles suburb of Santa Clarita. (AP Photo/Damian Dovarganes)
Los Angeles Sheriff Sheriff Alex Villanueva expresses his condolences for the victims of the shooting at Saugus High School at a news conference at the station Santa Clarita, Calif., Friday, Nov. 15, 2019. (AP Photo/Damian Dovarganes)