Fusako Petrus' friends hailed her as a hero after authorities say she was killed last week in Sacramento, California, while trying to save a friend

Fusako Petrus had her morning ritual.

Every day around 6 a.m., the 86-year-old Japanese immigrant would walk the track with friends at Highlands High School in Sacramento County, California. It was a good way, she said, to stay in shape and still indulge in her favorite Japanese rice crackers.

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Growing up in Japan in the ’30s, “She hadn’t had snacks before, and that was something she appreciated and loved,” says Twyla Rowe, whose mother was Petrus’ best friend. “Things were tough for her before and after [World War II].”

Friend Vicki Butler says much the same: “She experienced times in her childhood where she was hungry. … She would always have a plastic bag or container in her purse for leftovers.”

Petrus was also a devoted friend. After her husband, Alfred, died from Alzheimer’s in the ’90s, the retired cashier at Sacramento’s McClellan Air Force Base focused her attention on her aging neighbors and friends — helping them run errands, take out their garbage and chauffeur them around to appointments.

“She helped take care of other people,” Butler says. “What more can you ask of somebody?”

“Fusako lived her life being a dependable friend,” Butler says.

And according to authorities, that is how she died.

Image zoom Fusako Petrus

Victim Killed Protecting Friend

Investigators said that on Wednesday morning, about 6 a.m., the 4-foot-7-inch octogenarian rushed to the aid of her 61-year-old friend as the other woman struggled with an alleged assailant, 18-year-old Neven Butler, on the Highlands school track.

Petrus used her walking stick to try to fend Butler off, but he turned his attention toward her, investigators allege.

She was badly beaten in the attack and died at the scene. But her friend survived and was taken to the hospital and treated for her injuries.

“Anybody that tried to be there for their friend is what a hero is,” Rowe tells PEOPLE. “Fusako was there and did her best, even though it was probably impossible to prevail in something like that. He was a large cat attacking two kittens. There would be no chance.”

Butler was charged Monday with murder and two counts of assault with attempt to commit rape. Authorities have alleged that Butler’s assault was sexually motivated and that the two women were strangers to him.

The former Highlands High dropout and varsity football player is also charged with assaulting a 92-year-old woman later Wednesday, in a different part of Sacramento.

He is being held without bail at the Sacramento County Jail, and he has not yet entered a plea to his charges. His next hearing date is set for June 8.

His defense attorney, Linda Parisi, reportedly said he has “serious” mental health issues. “I do think that he is mentally challenged based on the information that I’ve developed,” she said, according to the Sacramento Bee. (Parisi didn’t return calls for comment.)

Image zoom Neven Glen Butler Sacremento Sheriff

One of Butler’s friends, Robert Hills, described him as a class clown who didn’t take school seriously, according to the paper.

Investigators told PEOPLE they zeroed in on Butler after he allegedly attacked the 92-year-old woman at a local elderly care home, where he was visiting a family member, on Wednesday after Petrus was killed.

“[Butler] just got up and, unprovoked, just started physically assaulting the 92-year-old female,” Sacramento County sheriff’s Sgt. Tony Turnbull alleged.

“He wasn’t hiding it,” Turnbull said, alleging. “He just started assaulting her out of nowhere. We were called, and we get there and he [was] still on the scene.”

‘She Made a Good Life’

Petrus lived in Sacramento County’s North Highlands community for five decades, her friends say. She met her husband in Japan just after World War II and came back with him to California, where he was stationed at McClellan.

“You have to be tough to leave your family, culture and language and go to a whole new country,” Butler says. “It takes a strong person. When they arrived here, it was after WWII. It was a tough time in the country to be Japanese.”

But, Butler says, “she made a good life for herself in America.”

Image zoom A make-shift memorial to remember Fusako Petrus is displayed on a fence surrounding the track at Highlands High School in Sacramento County, California. Rich Pedroncelli/AP

Petrus’ home was decorated with Japanese fans and masks, as well as bowling trophies she and her husband won. She also kept a collection of carefully folded shopping bags.

Six days a week, she would walk around the track with friends. “She felt secure in her neighborhood,” Butler says. “She was not afraid to walk this track whatsoever.”

Butler says the track was closed after the attack — a small memorial was reportedly erected there in Petrus’ honor — but she hopes that when it opens again that Petrus’ death doesn’t stop people from going there.

“I think she would be sad to know it wasn’t being used because of her death,” Butler says.