A 19-year-old man killed Tuesday when a fire destroyed his family's Blackhawk home suffocated from inhaling smoke, according to the Contra Costa County Coroner's Office.

Investigators believe Benjamin Litman and his father, Dr. Robert Litman, had little time to react to the late-night fire at their home in the 2900 block of Dear Meadow Drive. By the time the smoke detector went off, the fire was unchecked and growing rapidly., said Christina Jamison, fire marshal for the San Ramon Valley Fire Department.

Firefighters found Benjamin Litman's body inside the home when they arrived.

Robert Litman was found unconscious in a bedroom. He was taken by helicopter to Santa Clara Valley Medical Center to be treated for serious smoke inhalation, Price said. Litman was listed in critical condition Wednesday, said hospital spokeswoman Joy Alexiou.

The two men were the only people home at the time of the fire. A neighbor said the boy's mother returned home from the grocery store to find the home in flames.

Investigators believe the fire started in the attic and remained undetected until debris fell through the second floor ceiling. What caused the fire has not yet been determined.

The fire's cause has not yet been determined because of the amount of damage to the attic. The second story of the multimillion dollar home was destroyed.

There is nothing investigators found to indicate the fire was anything but accidental, Jamison said. The investigation is ongoing.

The blaze started at 11:15 p.m. Tuesday in the 2900 block of Deer Meadow Drive, said San Ramon Valley Fire District Chief Richard Price.

Benjamin Litman was a senior at Venture Independent Studies School in San Ramon. Principal Janet Terranova said he was a "great young man" and a bright student.

Although Venture is an independent study school and students spend little time on campus, she said "He was known not only by his own teacher, but by the other teachers as well."

The staff is looking at doing a memorial at the school for him in the fall, Terranova said.

A neighbor of the Litmans, who declined to give a name, called Benjamin "an incredible musician," who composed his own music and played classical piano, violin and guitar.

The neighbor said he planned to attend college in the fall.

"They are a wonderful, loving family and they have three beautiful daughters and Ben was their baby," the neighbor said.

Robert Litman, 62, is an allergy and immunology physician and practices in San Ramon.

"I've known Ben since he was 2 when they moved here," said Theresa Patterson, whose house is near the Litmans'. "Ben and his father were really close. Wonderful salt-of-the-earth people. They would do anything for a friend."

Pati Lawrence, who lives two houses from the Litmans, feared for her own safety after seeing flames shoot into the night sky above her 30-foot-high Redwood trees.

"I just saw a huge fireball," she said. "I prepared for evacuation because I thought it would go treetop to treetop."

Lawrence leashed her Havanese dog, packed her car and pulled it out into her driveway in case she had to escape quickly.

"We were so fortunate it didn't go through the whole neighborhood," Lawrence said, "because we're surrounded by grassy fields all around us and they're so dry."