A Napa grandmother, her two grandchildren and her boyfriend were killed in a house fire early Monday morning.

The blaze started around 5 a.m. in the 1400 block of Vale Avenue, in the Alta Heights area of east Napa.

Aurora Castanon, 58, Eutimio Torres, 37, Matthew Castanon, 12, and Giovanni Mendez, 4, were found unconscious at the scene.

All but Matthew were pronounced dead at the fire. The boy was pulled from the burning home and paramedics administered CPR while he was rushed to the hospital. He was taken to Queen of the Valley Medical Center and was pronounced dead on arrival.

The cause of the fire remains under investigation.

For Norma Mendez, the incident is an unspeakable tragedy. She lost her mother and two children.

On Monday afternoon, Mendez visited the scene of the blaze. Escorted by a Napa fire chaplain and a longtime friend, the grief-stricken woman roamed the fire-gutted living room and bedroom where her loved ones perished.

Family members waited for her outside. Crying, they held each other in their grief.

Mendez sat on the brick wall in front of the house, sobbing uncontrollably as Napa Fire and Police Chaplain Lee Shaw did his best to console her.

“My kids were there yesterday. They wanted to spend the night with her,” she said, referring to Aurora Castanon. “I was going to pick them up this morning and take them to school.

“Then around 5:30 a.m., a neighbor came to my house and said something tragic had happened. My boys loved to stay at their grandmother’s. My little Giovanni loved his Spiderman outfit. He wore it everywhere.”

Mendez also has a 2-year-old son, Alvaro. “I don’t think he knows what has happened. But I have to stay strong for him,” she said.

Castanon’s grandchildren stayed with her from time to time, according to neighbors. Matthew was a student at Alta Heights Elementary School.

Fire investigators said the home has a smoke detector. But as of early Monday, they could not confirm if the detector was working.

All of the victims were found in the same bedroom.

“The victims were in different places in the room. We don’t know if they were all in the bedroom when it started of if they gathered in there after the fire started,” said Napa Fire Capt. Scott Sedgley. The bedroom is adjacent to the living room, where the fire started and where the majority of fire damage occurred.

The victims most likely died of smoke inhalation, Sedgley said. “Smoke inhalation can knock a person out in seconds.”

At this point, fire officials do not know the fire’s cause, but do not suspect foul play.

The Napa/Solano Counties Arson Task Force was on scene most of the day, looking for clues on how the fire started, Napa Fire Capt. Jim Pope said.

Matthew’s father arrived in the early afternoon.

Pope said Aurora Castanon still had her Christmas tree. “And that it was in the room where the fire started.”

The blackened trunk of the tree rested against a neighbor’s fence.

A neighbor, who did not give her name, said Aurora Castanon had lived in the house for about 15 years.

“She was a professional house cleaner. I talked to her yesterday. She told me she has been really cold the past few weeks because her heater hasn’t worked for about three years,” the woman said. “I used to see her all the time and we would chat. I just feel numb.”

A neighbor across the street said Matthew was his stepson’s friend.

“They used to play together all the time. Her grandkids (spent) the night very frequently,” the neighbor said. “(Aurora) was a really nice person. A great neighbor. They were good people.

“I was sleeping when I heard what sounded like something hitting the side of the house. I got up and saw a neighbor banging on the door (of the house that was on fire.) It was then I could see the flames shooting out from the front windows,” he said. “This is just a terrible tragedy. I can’t believe it.”

While fires at homes occur with regularity, this is the first local fire in many years that took such a human toll. In January of 1999, a house fire on Yajome Street killed a Napa mother, her 2-year-old daughter and her 5-week-old nephew.