As firefighters worked to resuscitate Brittany Murphy Sunday morning, her husband, screenwriter Simon Monjack, was "literally in a daze," Murphy's West Hollywood neighbor Claire Staples tells

Monjack was in pajama bottoms and no shoes and looked "like he didn't know what was going on," Staples tells Us as his wife (who was found unresponsive Sunday morning in their bathroom) lay on a stretcher.

"They were pumping her heart trying to resuscitate her," Staples tells Us. "Then they brought her to the fire truck. They went to get paddles and were putting tubes down her throat."

But Staples says it seemed too late.

"She was really yellow," she tells Us. "They were holding her head back to keep the tube down her throat. She looked dead."

Staples recalls seeing Murphy's mother at the scene as well.

"She was carrying clothes for her," says Staples. "I don't think she realized how bad it was."

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Murphy, 32, was pronounced dead at 10:04 a.m. at Cedars-Sinai Medical Center in Los Angeles.

An official cause of death may not be determined for some time, since toxicology tests will be required, but "it appears to be natural," L.A. Assistant Chief Coroner Ed Winter tells Us. He said an autopsy is set to take place in the next two days.