A man suffering a heart attack died Sunday hours after District firefighters stopped at the wrong location and returned to their station in Northeast Washington, delaying treatment of the man by at least 20 minutes, according to relatives and a fire department spokesman.

Albert Jackson, 67, was pronounced dead at a Prince George’s County hospital shortly after he arrived by a D.C. ambulance, said his wife, Gloria Jackson, 65. In an interview Tuesday night, Jackson said she doesn’t know whether a faster response would have saved her husband.

“We tried to revive him here,” she said of efforts she and her grandson made to administer CPR while waiting for help for her husband. “They tried to revive him at the hospital. I don’t know if getting him there faster would have made a difference or not.”

Albert Jackson was a retired construction foreman who is also survived by three grown children, four other grandchildren and a great-grandchild.

The incident, first reported by Fox-5 news, is the latest in a long series of errors and delays in emergency response by the D.C. fire department, although such instances have been fewer under the District’s new administration, which just concluded its first year.

The fire department’s spokesman, Timothy J. Wilson, said the mishandled call is under internal investigation. The firefighters were assigned to Truck 17, based in Northeast Washington about 1.5 miles from the house where Jackson and his family have lived for the past 40 years.

Wilson said when firefighters arrived in the 400 block of 60th Street NE, they saw police with “what they presumed to be their patient on the ground. When they saw the patient didn’t need medical care, they went back to their quarters.”

[Infant transported to hospital in fire engine when no ambulance available]

Wilson said “they had assumed the call they saw was the call they were on” for the heart attack. But, the spokesman said, “that was not the actual call.”

D.C. Fire and Emergency Medical Services Chief Gregory M. Dean issued a statement Tuesday night offering condolences to the Jackson family.

“Going forward, the Department will require units to repeat the address to the dispatcher upon their arrival at a scene to ensure they are at the correct location,” the statement said. He added that the department and the Office of Unified Communications “are working to incorporate clear language” so that units “have more information on the call they are being dispatched to.”

The fire department said Truck 17, Engine 8 and Ambulance 26 were dispatched to Jackson’s house at 3:57 p.m. At 4:02 p.m., a dispatcher noted: “Engine 17 advises MPD [D.C. police] on scene. They are not needed.” That call from the truck in effect waved off the ambulance and the fire engine, which were en route. The dispatcher wrote, “No EMS needed.”

At 4:05 p.m., fire officials said the dispatch center received a second call from Jackson’s house. Emergency crews were again dispatched, and Ambulance 26 and Engine 8 — with an advanced paramedic aboard — arrived at the house at 4:16 p.m.

Gloria Jackson said she was on the phone with 911 while her grandson continued to administer CPR. “When they didn’t come right away,” Jackson said, “it didn’t dawn on me that time kept passing. I was wondering why the dispatcher kept asking me where they were.”

Edward Smith, president of the firefighters union, said he could not comment on specifics while the investigation is pending. He said firefighters “are not supposed to pass one emergency to go to another. They are obligated by duty to act.” But he also said he did not know whether that circumstance applied to this case.

The incident is yet another problem for the D.C. fire department that has been hampered by emergency-response delays. Many incidents occurred in 2014 and predate the current chief, Gregory M. Dean, although some have occurred under his watch. Many of the delays have been attributed to problems with dispatching, computer glitches and too few ambulances.

In July, a D.C. fire lieutenant was charged with neglect of duty for failing to alert emergency dispatchers in March that he was just down the street from a child who later died after choking on a grape.