TACOMA, Wash. - A raging house fire that killed a woman and left her husband fighting for his life began with a deafening explosion in the middle of the night that was obviously meant to kill, say neighbors.

They are convinced that the blaze was a deliberate attack - a planned murder of the couple who lived there - although they have no idea who would want to do it.

"I've never heard any explosion that loud in my life," says Timothy Worrell, who lives near the house, which burned so fiercely that the raging flames clawed all the way to the tops of surrounding trees.

Worrell is convinced someone set off a bomb in the house. Fire investigators say the fire, at 7202 S. Lawrence St. in South Tacoma, is "suspicious."

Worrell said he leaped out of bed when he heard the explosion and ran down the street.

"There were fireballs coming up in the air," he says.

He saw his neighbor, on fire, running back inside the burning home to get his wife. So Worrell ran in, too.

"I crawled probably for about seven or eight feet yelling for his name - but I decided to exit the house due to the fact that there was an enormous odor of gasoline," Worrell says.

Investigators won't say if those fumes came from an accelerant or an explosive device. But they do say everything about this fire is suspicious.

When crews arrived, at about 3:25 a.m. Sunday, they also found a fifth-wheel trailer engulfed in flames next to the home, said Tacoma Fire Department spokesman Joe Meinecke.

Several neighbors told KOMO News they have no idea why someone would want to harm the couple who lived at the house - but they do say it has happened before.

Residents in the area said they've witnessed four different fires at the home in previous years - and they always seem like they happen around Christmas or New Year's.

This time the owner of the home was severely burned. Medics rushed him to Harborview Medical Center, where he is still fighting for his life.

His wife died inside the home. She was found by a search-and-rescue team who responded to the blaze.

The wife's sister and father watched the aftermath of the blaze in disbelief, and said they don't know who would want to do such a horrible thing.

Worrell said he doesn't know why anyone would want to hurt his neighbors. He says the wife stayed at home while the husband worked as a contractor.

"The (killer) did it to one of the nicest people that you could ever imagine," he says.

Investigators combed the scene all day long. But so far they have not identified the victims or say what evidence they have gathered.

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• More photos of the deadly house fire »