FREMONT — New details have emerged surrounding the tragic home fire that killed Feda Almaliti, the nationally-known advocate for people with autism, and her 15-year-old son Muhammed early Saturday.

Almaliti, 43, had safely escaped the blaze along with two others, but went back into the burning home to get her son, according to a statement the Fremont Fire Department issued Tuesday evening.

A little before 2 a.m. Saturday, before firefighters had arrived at the home, a woman and a girl — who those close to the family have told this news organization are Almaliti’s sister and niece — escaped the home along with Almaliti.

When Almaliti realized her son was not with them, she “bravely re-entered the residence in an attempt to rescue him as flames and heavy smoke rapidly advanced from the first floor to the second floor,” the department statement said.

Fire crews “began an aggressive interior attack with simultaneous search and rescue efforts,” and they located Almaliti and Muhammed together on the second floor in a rear bedroom.

“Both victims sustained life-threatening injuries, were rescued by firefighters and transported to a nearby hospital. Despite persistent lifesaving efforts by Fremont Fire and Falck paramedics, both victims died,” the statement said.

“This is a tragic and heartbreaking incident,” Fremont Fire Department Chief Curtis Jacobson said in the statement. “Feda Almaliti courageously risked her life to save her son’s. Her actions were selfless and valiant.”

Fire officials said investigators have determined the one-alarm fire started in the kitchen area of the home, though its cause is still under investigation.

Firefighters responded to the fire at 1:44 a.m., and “arrived within minutes to a two-story residence with heavy smoke billowing out of the front door and fire showing from the rear of the property.”

The fire was fully contained and extinguished within 25 minutes of firefighters arriving, the department said.

Almaliti and her son are the first fire-related deaths in the city since 2010, the department said.

In the effort to contain the fire, one firefighter was injured and taken to the hospital for medical evaluation, and released a short time later.

Almaliti’s sister and niece were also transported to a nearby hospital for non-life-threatening injuries, the department said.

Friends and colleagues said Almaliti was a fierce advocate for people with autism and their families. Inspired by her own son and the children of friends, Almaliti helped change California law.

She and a core group of parents of children severely afflicted by autism spearheaded the effort behind SB 946, a bill authored by then-state Sen. Darrell Steinberg which went into law in 2012 and requires insurance companies to cover treatment for autism.

She served on a host of boards for agencies that support autism advocacy, research and treatment efforts, including the National Council on Severe Autism, and the Autism Society of the San Francisco Bay Area.

“She was a very powerful force in reshaping autism-related policy in our state, but she knew that there were miles to go. She knew that it was just the start,” Jill Escher, the president of the National Council on Severe Autism said Saturday about her friend Almaliti.

“She knew that we needed to do so much work as a community to help this growing population affected by autism,” Escher said.

“There’s just going to be a huge hole in our hearts forever,” Escher said. “People just adored her.”