By Elizabeth Wolfe, Natasha BertrandHaley Britzky and Pete Muntean, CNN

CNN — 

Four first responders who arrived at the scene of Sunday’s fatal private plane crash near Raphine, Virginia, told CNN the plane left a “crater,” and they believe it impacted the ground at a very steep angle.

The first responders, who spoke on the condition they not be identified, described a grisly scene. There were perhaps four recognizable pieces of wreckage from the plane, they said. “There was nothing really bigger than your arm,” one said.

The responders also found signs of human remains.

Federal officials are investigating the crash of the unresponsive plane that flew near the US Capitol region on Sunday, prompting military fighter jets to rush to intercept the aircraft before it went down in northern Virginia, leaving no survivors, authorities say.

Investigators from the National Transportation Safety Board are expected to arrive at the crash site Monday, where they will “begin the process of documenting the scene and examining the aircraft,” the agency said in a statement.

The civilian aircraft, which had four people on board, missed its destination by more than 300 miles before plunging to the ground in Virginia Sunday afternoon, sources familiar with the investigation said.

The small plane took off from an airport in Elizabethton, Tennessee, and was headed for New York’s Long Island MacArthur Airport, a statement from the Federal Aviation Administration said.

No surviving passengers were found at the crash site Sunday night, Virginia State Police said, noting their identities will be released when they become available.

The details of why the plane veered so far off course and what caused the crash are still unclear.

The US Capitol complex was placed on an “elevated alert” when the plane flew near the area on Sunday afternoon, according to a statement from US Capitol Police.

F-16 fighter jets were “authorized to travel at supersonic speeds” as they raced to make contact with the aircraft, a Cessna 560 Citation V, according to a release from the Continental US North American Aerospace Defense Command Region.

The jets’ extraordinary speed caused a sonic boom across the Washington, DC, area, officials said, and some residents reported being startled by the sudden and resounding sound.

“The house rocked, the windows rattled, and it was done like that. We were obviously freaked out a little bit,” Chuck Martin, who felt the boom in Fairfax County, Virginia, told CNN affiliate WJLA. “I started calling the police. Their nonemergency line was busy forever. When I finally got through, they said, ‘Oh this DOD aircraft went supersonic, which sounded a little bit strange.’”

Residents in Maryland also reported hearing the boom.

“Our Ring notifications were going crazy with so many different options. Was it the Navy? Or was it a sonic boom? Or was it an earthquake?” Sandy Abuarja, who lives in Gambrills, Maryland, told CNN affiliate WBAL.

When the F-16s reached the Cessna around 3:20 p.m., the jet pilots set off flares in an effort to get the pilot’s attention, the release said.

“The pilot was unresponsive and the Cessna subsequently crashed near the George Washington National Forest, Virginia,” the release said. “NORAD attempted to establish contact with the pilot until the aircraft crashed.”

The F-16s did not shoot down the aircraft, a US official told CNN. The official noted that it is typical for the FAA to call in jets if someone is flying unsafely.

State and local police in Virginia searched the area for hours after being notified of a possible crash near the northern city of Staunton, the agency said.

No survivors found in the wreckage

None of the plane’s passengers were found alive when first responders reached the crash site around 8 p.m. Sunday night, state police spokesperson Corinne Geller confirmed.

The private aircraft is registered toEncore Motors of Melbourne, Inc., a company based in Florida, according to FAA records.

John Rumpel, whose wife Barbara is listed as the president of the company, told CNN that they own Encore. The husband confirmed Barbara Rumpel is safe, but declined to comment further.

John Rumpel told The New York Times that his daughter, a 2-year-old granddaughter and her nanny were onboard the plane. He told the Times that the family was returning home to East Hampton, New York, after a four-day trip to his home in North Carolina.

On her Facebook profile, Barbara Rumpel commented, “My family is gone, my daughter and granddaughter,” on an unrelated post in which others were asking if she was on the plane.

Plane flew near US capital area

As the plane veered off course Sunday afternoon, it passed over Washington, D.C, and was not responding to efforts to make contact, prompting the F-16 fighter jets to respond.

US Capitol Police placed the Capitol Complex on an “elevated alert” as the aircraft passed through the region, the agency said.

“This afternoon, our officials were working closely with our federal partners to monitor an unresponsive pilot who was flying an airplane near the National Capital Region. The U.S. Capitol Complex was briefly placed on an elevated alert until the airplane left the area,” a statement from the department said.

It’s unclear whether the aircraft entered restricted airspace.

President Joe Biden was golfing at the Andrews Air Force Base golf course near Maryland’s Joint Base Andrews when the sonic boom resounded through Washington. The US Secret Service said it did not alter its posture for keeping President Biden secure after the fighter jets were scrambled.

The president was briefed on the incident, according to a White House official.