On his first day on the job as a firefighter in Southeast Washington, John A. Donnelly Sr. responded to calls for a baby being born, a shooting, a fire and a person suffering a heart attack.

It was October 1992, and he was on Truck 16 in Garfield Heights.

“I knew then that this was where I wanted to work,” Donnelly said of the District.

He moved up through the ranks — assigned to an elite rescue truck, then promoted to battalion chief, and on up to the executive office. He earned the department’s highest honor for rescuing an unconscious man trapped in a burning house.

In September, Mayor Muriel E. Bowser (D) announced that the 54-year-old Donnelly was her choice to be the District’s new chief of the Fire and Emergency Medical Services Department. Donnelly did not predict drastic change, saying at a news conference: “Our path forward is the path we have been on.”

The District’s new fire chief is signaling a continuation of policies and plans put in place by his predecessor, Gregory M. Dean, whom the mayor lured out of retirement from Seattle in 2015 to turn around what was then a troubled agency marred by high-profile failures. Donnelly was one of the insiders Dean turned to for help.

But Donnelly — who started fighting fires for a volunteer company in Prince George’s County when he was 16, and later battled forest and brush fires in remote areas of the West Coast — faces some daunting challenges.

He assumes the role in the midst of a global pandemic that has sickened more than 285 D.C. firefighters, including himself, and sidelined many more in quarantine. D.C. leaders warn that his department will not be immune to budget cuts forced by a fall in revenue and expenditures because of covid-19.

“There is a crisis in front of us,” D.C. Council member Charles Allen (D-Ward 6) told Donnelly at his brief confirmation hearing in December, which drew just two other lawmakers and the supportive president of the firefighter’s union.

“You’re under incredible stress every day, and throw on top of it the pandemic,” said Allen, who chairs the Committee on the Judiciary and Public Safety.

“The last nine months have been really hard,” Donnelly answered, noting that one of his most important jobs is ensuring that first responders have enough masks and other protective equipment.

Emergency calls during the coronavirus pandemic have decreased, he said, corresponding to a decline in the numbers of workers and tourists who can more than double the District’s population on a typical workday. But he said first responders falling ill or being forced into quarantine means their colleagues are working harder to fill vacant shifts.

He said paramedics are finding more people dying at home — in many cases not of covid-19. It is a phenomenon seen across the country, partly attributed to people’s being afraid to seek treatment at hospitals during the pandemic.

Donnelly lives in Manor Park in Northwest Washington with his wife, a city schoolteacher. They have a son who is a U.S. Army captain serving in Kuwait, a daughter studying to be an emergency medical technician in New York City and another son in high school. In his spare time, Donnelly volunteers with the Boy Scouts in the Brookland neighborhood of Northeast Washington.

Not only was Donnelly among the first of the District’s firefighters to contract covid-19, he donated his blood plasma in the search for treatments, and he later was among the first to be vaccinated against the novel coronavirus.

For him, the tumult brought on by the virus has an upside. “Relationships built under stress,” he said, “are the ones that last.”

Donnelly started his firefighting career while still in high school, at the Allentown Road Volunteer Fire Company in Fort Washington, in Prince George’s County.

Still in his teens, he was struck by encountering people of different backgrounds, assembled in one place with a common goal of “helping the community.”

Two years later, he traveled to the West Coast, arriving in Cedarville, Calif., near the border with Nevada and Oregon — “an hour and a half from a traffic light” — with fire boots made for service in a city. He had to switch to gear more suitable for hiking as he set off to confront his first forest fire, which was ripping through 30,000 acres outside Reno, Nev.

He did not perform well.

Donnelly said he was acting like a whiny teenager, and the fire commander threatened to send him home.

He turned himself around.

“Boy, did he help me grow up,” the chief said. “It was a lesson, and I was not going to be a failure.”

Donnelly returned home a short time later, taking firefighting jobs in Prince George’s County and later at Reagan National Airport, before coming to the District in 1992. He helped during the Sept. 11, 2001, attacks, commanded the EMS response to the mass shooting at the Navy Yard and at the four-alarm fire that burned the landmark Frager’s Hardware on Capitol Hill in 2013.

While working for the fire chief who preceded Dean, Donnelly was called on to help straighten up a department experiencing failures that led to delays in getting help to people in emergencies.

They included firefighters ignoring a man dying of a heart attack across the street from their station, an ambulance assigned to a presidential motorcade running out of gas on the White House grounds and a police officer lying injured on the street while waiting too long for help.

Donnelly took on the unglamorous job of managing a fleet, then in disarray, with nearly half the department’s firetrucks, engines and ambulances in disrepair or running without safety certificates. Firefighters were climbing ladders that had not been inspected, and help was not reaching people fast enough.

Donnelly continued helping to improve the department when Bowser became mayor and hired Dean as chief. The two worked to restore credibility, and at his December confirmation hearing, Donnelly told lawmakers that for the first time in five years, “every one of our apparatus that are in service are certified.”

That means, Donnelly said, the vehicles “stay in your community so they can help you when you need it.”

Donnelly carefully answered questions from council member Brooke Pinto (D-Ward 2) about lingering problems with dispatchers at the Office of Unified Communications, a separate D.C. agency also known as the 911 center. Firefighters have struggled recently with being sent to wrong addresses, which slows their response to critical emergency calls.

Donnelly did not assess blame, and in a later interview, he said there are “challenges we both face to get the system working to get the best outcome for all patients.” In late December, the mayor’s office announced that the director of the 911 center, Karima Holmes, was leaving for another job, and a national search for her replacement is underway.

The new chief said he plans to build on programs put in place under Dean, including “hands-on” CPR training given to tens of thousands of D.C. residents and workers. The technique is popular because it eliminates mouth-to-mouth resuscitation and emphasizes chest compressions to quickly pump blood to an oxygen-deprived brain. He said the cardiac arrest survival rate has doubled since 2014.

Dean and Donnelly developed a program in which nurses at the 911 center talk to patients calling in for help, diverting some away from hospitals and cutting back on unnecessary responses by EMT teams. Next year, Donnelly said, he wants to improve treatment for stroke patients and track their progress to determine whether paramedics can adjust their care to improve outcomes.

Donnelly has been busy instilling core values that include first-responders thinking on their own.

“Instead of having a rule for everything,” he said in an interview, “let’s have a framework for making decisions. That’s when we’re at our best, when people have the flexibility to do what’s right.”