The Cessna Citation slammed into mountainous terrain Sunday afternoon in Virginia, some 170 miles (275 kilometers) southwest of Washington, killing all four people aboard, officials said.

The North American Aerospace Defense Command (NORAD) said F-16s were dispatched to intercept an "unresponsive Cessna 560 Citation V aircraft over Washington, DC, and northern Virginia."

NORAD said flares were deployed to try to draw the attention of the pilot but there was no response and the private plane eventually crashed near the George Washington National Forest.

"NORAD attempted to establish contact with the pilot until the aircraft crashed," it said in a statement.

The F-16s triggered a sonic boom across Washington and its suburbs, startling residents and rattling windows for miles.

"The NORAD aircraft were authorized to travel at supersonic speeds and a sonic boom may have been heard by residents of the region," NORAD said.

Aviation experts speculated that the Cessna pilot may have become incapacitated due to a depressurization of the aircraft, which can cause a rapid loss of consciousness at altitudes above 10,000 feet (3,000 meters).

A loss of cabin pressure was blamed for a high-profile 1999 Learjet accident that killed golfer Payne Stewart and four other people.

In that case, the Learjet, which was on a flight from Florida to Texas, flew for hours for thousands of miles on autopilot before eventually running out of fuel and crashing in South Dakota.

The Federal Aviation Administration (FAA) and National Transportation Safety Board said they were investigating Sunday's accident.

Virginia State Police said in a statement that first responders reached the crash site near the town of Staunton by foot some four hours after the Cessna plummeted to the ground.

"No survivors were located," police said.

The plane had taken off from Elizabethton, Tennessee, bound for Long Island MacArthur Airport in New York, the FAA said.

But it turned around after flying over Long Island and headed back south over Washington and into Virginia, climbing as high as 34,000 feet, according to flight tracking website Flightradar24.

President Joe Biden, who was at the White House and also played golf Sunday, was briefed on the incident, an official said without specifying whether any emergency precautions were implemented.

US authorities have yet to officially identify those on board, but comments by two relatives of people believed to have been on the plane provided some information.

Public records showed the aircraft was registered to Florida-based company Encore Motors of Melbourne, whose owner John Rumpel told The Washington Post his "entire family" was onboard, including his daughter, a grandchild and her nanny.

In response to condolence messages on her Facebook page, Rumpel's wife, Barbara, wrote on the platform Sunday night: "My family is gone, my daughter and granddaughter."