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) — A 16-year-old boy who killed two students and wounded three others at his Southern California high school before turning a gun on himself died Friday without investigators discovering the motive for the attack, authorities said.

Nathaniel Tennosuke Berhow, died from a head wound. His mother was present when he died, according to a Los Angeles Sheriff’s Department statement.

Berhow, described by friends as quiet but funny and likable, showed no outward signs of violence prior to the attack. After more than 40 interviews, police still don’t know what prompted him to commit such a crime, said Capt. Kent Wegener of the department’s homicide unit. He said no manifesto, diary or suicide note had been found.

“It still remains a mystery why,” Sheriff Alex Villanueva told a press conference. He said it was “a planned attack, it was deliberate,” but “we don’t have” the details behind it.

Berhow opened fire around 7:30 a.m. Thursday, his birthday, after being dropped off at Saugus High School in the Los Angeles suburb of Santa Clarita. Video surveillance showed Berhow walk alone to the center of a quad, drop his backpack, pull out the gun and start firing, police said.

Villanueva said after opening fire Berhow “cleared a malfunction” with the gun and kept shooting. He counted his rounds, Villanueva said, firing about six shots and using the last bullet on himself. The attack took just 16 seconds.

“As far as we know the actual targets were at random,” the sheriff said.

Villanueva said the conclusion that the attack was planned was based on Berhow bringing the weapon, ably handling it and keeping track of the rounds fired.

“It wasn’t a spur-of-the-moment act,” Villanueva said.

Three off-duty law enforcement officers were first on the scene and treated some of the wounded until paramedics arrived.

The dead were identified as 15-year-old Gracie Anne Muehlberger and 14-year-old Dominic Blackwell.

In a statement, 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.

“We miss her smile, laughter, sweet kisses, and her amazing sense of humor. We will even miss her constant pestering for Starbucks and Cold Stone and anything else with lots of sugar in it. It must have been the reason why she was so sweet.”

Two girls wounded in the attack, 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.

The names of the wounded were not released.

Berhow was described as a quiet and smart kid who was a Boy Scout and had previously run track for his school.

“You have the image of 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.”

In fact, the stereotype of the loser sociopath is often inaccurate, according to the psychologist who co-wrote federal guidelines for assessing school shooting threats and has interviewed five shooters. 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, according to Marisa Randazzo, a former chief research psychologist at the U.S. Secret Service.

“These are acts of suicide as much as homicide,” said Randazzo, who is now CEO of a firm that does threat assessments.

Most shooters she studied were academically successful and weren’t social outcasts.

Friends said while the boy could be introverted, he had a girlfriend and good social network focused on his cross-country teammates.

Randazzo said she expects investigators eventually will learn that someone had an inkling of trouble.

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 Bureau of Alcohol, Tobacco, Firearms and Explosives is working with police to determine where Berhow got the handgun used in the attack.

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Antczak reported from Los Angeles. Justin Pritchard in Los Angeles also contributed to this story.

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This story has been corrected to show that Marissa Randazzo co-wrote federal school shooting threat guidelines rather than being the sole author. It also corrects the number of shooters she’s interviewed to five, not 10.

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)