The biggest question is whether it was set intentionally. Vallejo police haven't said anything but they have a continued presence at the home.
A 5-year-old boy is dead, his mother terribly burned and neighbors have many questions.
Vallejo police are now looking into a fatal house fire that happened over the w/e. Was it arson? A 5yo boy died. pic.twitter.com/V4z2c9168W— Amy Hollyfield (@amyhollyfield) May 23, 2016
Seeing their street roped off with crime tape just added another layer of emotion for neighbors.
"Hits me hard, kinda scares me that somebody would do that with kids in the house. I really don't know what to say," neighbor James Hughes said.
"It's a tragedy. I have five kids, to have somebody burn a child, a family, alone just a family, what is this world coming to?" asked neighbor Markell Wallace.
The fire happened Sunday morning just before 10 a.m.
The mother suffered second and third-degree burns trying to rescue her child. Neighbors also tried to get him to safety.
"I hosed her off really good, just kind of cooled her off then asked her where the baby was and started to go in. I could only get like halfway through the living room," neighbor Jeffrey Ames said.
Vallejo police have not said officially whether they think someone set this fire, but the fire department won't comment, saying the case belongs to the police.
Police stationed officers in front of the home overnight to protect the scene.
Neighbors say there has been some changes recently at the home. "She just had a boyfriend move in, and ever since then, that's when things went bad, I will say that. A lot of things have just been going on over there, so I'll leave it at that," Hughes said.
An investigator says he is hoping police will be able to release more information later today.