e Joslin Diabetes Center at the Hospital of Central Connecticut, survived the attack and staggered from the burning house with what a neighbor described as a bloody head wound. He was hospitalized in stable condition.

Law enforcement officials in Cheshire, a prosperous suburb 15 miles north of New Haven, declined to identify the two men who were in custody, or the charges against them.

Neighbors of the Petits on Sorghum Mill Drive, in a subdivision of tall trees and manicured lawns, described a chilling sequence yesterday. They said the family’s house was suddenly engulfed in flames, police cars converged, and two young men — one with a shaved head and the other with closely cropped hair — ran from the house and tried to flee in one of the family’s vehicles.

“In Cheshire, we are not used to this type of event,” said Michael Cruess, the town’s police chief. “It’s very tragic, and it is probably going to reach right down to the roots of this community.”

The authorities said that Dr. Petit’s wife of 22 years, Jennifer Hawke-Petit, 48, and two daughters, Hayley, 17, and Michaela, 11, were declared dead at the scene after the police and firefighters arrived at the home shortly after 9:30 a.m.

Ms. Hawke-Petit was co-director of the health center at the Cheshire Academy, a boarding and day school.

Hayley graduated in June from Miss Porter’s School in Farmington, and planned to attend Dartmouth, her father’s alma mater. Michaela was to enter the sixth grade at the Chase Collegiate School in Waterbury.

The authorities said that two men showed up at the Petit house early yesterday, but that it was unclear how they gained entry or what happened inside about 9 a.m. But at that point, the police said, either the mother or the 17-year-old daughter accompanied one of the two assailants in a family car to a local Bank of America branch, where she withdrew an undisclosed amount of cash.

“Bank employees were suspicious enough to contact the Cheshire Police Department, who immediately went to the bank and the victims’ residence to intercept the vehicle involved,” said Lt. J. Paul Vance of the Connecticut State Police.

He declined to comment on a report on The Hartford Courant’s Web site that Ms. Hawke-Petit had appeared at the bank and managed to slip a note to a bank employee that her family was being held hostage.

Details of what followed remained unclear yesterday, and law enforcement officials in Connecticut declined to comment on several questions about the case pending charges against the two men and their arraignment scheduled for today in State Superior Court in Meriden. They said autopsies would also be performed today by Connecticut’s chief medical examiner, and refused to discuss any evidence or whether the deaths resulted from the fire or an assault.

Lieutenant Vance said the first police officer to arrive at the Petit house saw that it was on fire and saw two men trying to flee in a car. When the officer tried to block the men, they rammed his police cruiser, Sergeant Vance said.

The officer then called for help, and fellow members of the Cheshire Police Department positioned two more police cars nose-to-nose as a barricade a few houses away.

A neighbor, Anton Rao, an optometrist who described himself as a close friend of the Petits’, said the two men drove into the police barricade at close to 60 miles per hour, and crashed through it before their car broke down and came to a halt.

Dr. Rao said he was on his way home about 9:30 a.m. when he saw the police with rifles outside the Petit house. He said he parked his car and continued on foot along a path in the backyards of the subdivision to reach his own house. “I told my own kids to go to the basement and lock the doors,” he said yesterday, choking back tears.

Yesterday afternoon in a drenching downpour, more than a dozen neighbors huddled under umbrellas along the family’s street, consoled one another, and tried to fathom what had descended on the Petits.

“Something must have gone terribly wrong because these people would give away everything they had,” said Kim Ferraiolo, 37, who lives next door.

She said her three children, ages 3, 4 and 7, had frequently played unattended with Michaela Petit in the two families’ yards. “I think that is probably going to change for a while,” she said.

The neighbors said the Petits were a busy family, but retained a balance in their lives. Ms. Hawke-Petit, who once worked as a nurse at Yale-New Haven Hospital, joined the staff of the Cheshire Academy to work with young people, they said. She and her husband also devoted time to a youth group at their church, neighbors said.

Dr. Petit was in stable condition yesterday at St. Mary’s Hospital in Waterbury, according to a hospital spokesman.

While keeping a demanding schedule for his medical practice, the neighbors said, Dr. Petit was often seen pruning, arranging and tinkering around the yard of the family lawn. Besides his hospital position, Dr. Petit is president of the Hartford County Medical Association and has written extensively on endocrinology.

Colleagues at the Hospital of Central Connecticut said they learned of what had happened to Dr. Petit and his family shortly before noon yesterday.

“It think it’s not sinking in quite yet,” Laurence A. Tanner, president of the hospital, said in an interview.

He added: “Dr. Petit is an incredible doctor. He’s not only dedicated to his patients, but he’s a teacher and a researcher.”

Both of the Petit daughters were described as outgoing and popular.

“Michaela, our fifth grader, was bright, very high-achieving, a confident, happy girl,” said John Fixx, headmaster of Chase Collegiate. “She brightened every day.”

At Miss Porter’s, Hayley had run cross-country, played basketball, was co-captain of the crew team and worked to raise money for multiple sclerosis research.

Burch Ford, the school’s headmistress, said yesterday that the younger children “really looked up to her.”

“It’s just unspeakable, a horribly senseless tragedy,” she said.

Kristin Hussey contributed reporting.