Montgomery County Police Chief Bernard D. Crooke Jr., 54, died yesterday, shortly after he suffered difficulty breathing and lost consciousness while recuperating at home from intestinal surgery he underwent 11 days ago, officials said.

Crooke, widely praised for restoring stability to a department troubled by dissension before his arrival in 1979, died about 1:30 p.m. in the emergency room of Shady Grove Adventist Hospital in Rockville. The physician who treated him, Dr. Steven Gevas, said that Crooke probably died of a heart attack or a massive blood clot in one of his lungs, but added that an autopsy would be needed to pinpoint the cause of death.

"This is one of the saddest duties I've ever had to perform," Sgt. Harry Geehreng, a police spokesman, said, fighting tears at a news conference called to announce the chief's death.

Crooke was credited by county officials and police union leaders with stabilizing the 750-member department through his quiet, even-handed approach to law enforcement in a suburban county that has prided itself on a low crime rate and has struggled to cope with the problems of growth and urbanization.

Crooke guided the police force as the county began grappling with the pressing need to expand police manpower to serve the booming upper county. He also oversaw creation of the "jump-out" squad formed last year to combat a growing drug problem, primarily in communities inside the Capital Beltway.

Crooke's sudden death stunned those who knew him and brought an outpouring of solemn praise for a veteran police officer who began his career as a Washington patrolman 32 years ago. He rose to the No. 2 job in the Metropolitan Police Department at a time when the department was being reformed.

But Crooke, as a ranking white officer in the District, was given little chance of becoming chief when the city was making the transition to black political leadership. He retired from the D.C. police in 1979 to take the Montgomery job.

His death "is a terrible tragedy," said former county executive Charles H. Gilchrist, who hired the low-keyed Crooke after firing his predecessor, Robert J. diGrazia. DiGrazia's flamboyant manner and public criticism of officers had made him an ineffective leader, Gilchrist said.

Deputy Police Chief Donald Brooks, who has been the acting chief in Crooke's absence, called him "a superb leader" who had improved the morale and performance of the department.

County Executive Sidney Kramer said that "Chief Crooke was a highly respected member of my staff and, even more importantly, a good friend . . . . He enjoyed the admiration not only of his colleagues but also of those police officers who followed his command."

The County Council stopped its meeting for a moment of silence at 2:34 p.m. after Council President Michael L. Subin delivered the news of Crooke's death. Kramer ordered county flags lowered to half staff.

Walter Bader, president of the county chapter of the Fraternal Order of Police, said he and Crooke "developed a real friendship" despite their professional differences. Although Crooke disagreed with him frequently, Bader said, Crooke fundamentally supported the existence of the union, which won collective bargaining rights in a voter referendum one year into Crooke's administration.

"I'm going to miss that friendship," Bader said. "We would posture on things, but we could have arguments in private and walk out the door and joke with each other."

Takoma Park Police Chief A. Tony Fisher, the first black chief in Montgomery and a former county detective under Crooke, praised the chief for displaying "a great deal of sensitivity in the area of minority representation."

"He never came across as a macho kind of guy, never came across as overpowering," said Fisher, who was formerly president of the department's Coalition of Black Police Officers.

Friends said his reserved manner helped carry Crooke, the son of a homicide detective, up the ladder of police command in the District.

"He had the quality of evenness of judgment," said former D.C. police chief Jerry V. Wilson, a close friend. "He had a good, solid ability to judge things evenly, not to get too excited, to separate the wheat from the chaff, so to speak."

On Feb. 10, after not feeling well for several days, Crooke "had some sort of attack," Deputy Chief Brooks said at yesterday's news conference. His wife, Joyce, drove him to Suburban Hospital, where he underwent surgery three days later.

Crooke was discharged Monday from Suburban Hospital in Bethesda after surgery to remove part of his small intestine, and was said to have been in good spirits after returning to his Montgomery Village home. But he developed trouble breathing about noon yesterday and soon lost consciousness, Geehreng said. By the time he arrived by ambulance at Shady Grove Adventist, emergency workers were using cardiopulmonary resuscitation to keep his heart beating.

Gevas said he worked for 35 to 40 minutes with various medications in an effort to make Crooke's heart pump on its own.

"We did everything we possibly could do," Gevas said, "but we had no electrical activity from his heart, no matter what we did."

He said he could not determine immediately whether Crooke's death was related to the surgery he underwent Feb. 13 to relieve what a department spokesman said was "an intestinal blockage." He said he was unfamiliar with the chief's medical history, but called the operation "fairly common."

Brooks, who remains acting chief, said that he, Kramer and Robert S. McGarry, director of the county's Transportation Department, visited Crooke at his home on Monday and were "amazed at how good he looked."

The chief was in fine spirits, resting on his living room sofa.

"I had also seen him Sunday, and I was amazed at how much better he looked on Monday," Brooks said. "In fact, I teased him a little about the rapid recovery. We were all thrilled."

Besides his wife, Crooke is survived by three sons, Douglas, Eddie and Chris, and a daughter, Tina.

Staff writers Jo-Ann Armao, Beth Kaiman and Claudia Levy contributed to this report.