Mayor Bloomberg was woken up Monday morning at 5 a.m. with a call that a police officer, Dillon Stewart, had been shot.

By 6 a.m. he was out of his Upper East Side townhouse and deep in Brooklyn at Kings County Hospital, being briefed on Stewart’s condition and on the investigation.

Yesterday, Mr. Bloomberg offered his most detailed account yet of what happened behind the waiting-room doors before Stewart died at about 8:40 a.m. and before he and the police commissioner, Raymond Kelly, held a news conference about the crime.

He said the doctor “actually said and thought that the officer had a better than 50-50 chance to make it,” but that Stewart subsequently suffered a “series of heart attacks.”

“Everything that modern medicine could do was done,” Mr. Bloomberg told reporters when asked how the morning unfolded. The mayor said he was directly outside the room as doctors tried to resuscitate Stewart’s heart one last time. When Stewart died, it was the mayor, acting as the city’s ambassador, who took Stewart’s wife, mother, and sister to see his body.

“None of us can ever replace a family member,” the mayor said. “None of us can ever say what they all want to hear. They all want to hear so-and-so is not dead, is coming back … that’s the one thing the mayor can’t say.”

Stewart, a decorated police officer, was shot at 3 a.m. Monday while pursuing a car that ran a red light in East Flatbush, Brooklyn. Allan Cameron, 27, was arrested and charged with two counts of murder and criminal possession of a weapon. Mr. Cameron was also charged with attempted murder, robbery, assault, and criminal possession of a weap on in the November 19 shooting of Officer Wiener Philippe.

Mr. Bloomberg, who has long been in favor of strengthening gun control laws, said yesterday the federal government needs to do more to prevent guns from “flooding” into the city’s streets.

“What we need is national legislation to stop this craziness,” he said. “We have more guns in America than we have people.”

He added: “I don’t know how many people have to die or how many police officers have to die before we realize that the right to bear arms is one thing,” but that “people walking around with guns under their coats, and even teenagers doing this, it’s just insanity.”

Last month, Congress gave final approval to a bill that shields gun manufacturers and dealers from liability in gun crimes. The law had support from the gun industry, but was denounced by gun control advocates.