A family said they saw the missing F-35 fighter jet flying upside down at just over 100 feet before it crashed

• A family in South Carolina said they spotted the missing F-35 flying almost inverted.
• They told NBC News they were celebrating a birthday when they saw the aircraft at about 100 feet.

A family in South Carolina said they saw the F-35 jet that went missing this weekend just before it crashed, and noticed that the aircraft was almost inverted and oddly close to the ground.

The Truluck family told NBC News they were celebrating their son's seventh birthday in Williamsburg County on Sunday when they saw the jet and then heard a "boom."

Stephen Truluck said they could see the "canopy" of the aircraft, and that it was about "three quarters" upside down, per NBC News.

His wife, Adrian Truluck, estimated that the jet was "probably 100 feet above the tree tops."

"Our kids always give a little salute, so we said: 'Look at the plane. Oh my gosh, it's so low,'" she told NBC News.

Since they were about 60 miles from Shaw Air Force Base, they didn't think anything was amiss at the time, the outlet reported.

F-16s often use the area for training, and are sometimes spotted practicing flare-outs and simulated dogfights, Stephen Truluck told Charleston-based paper The Post and Courier.

He added that the jet was flying northeast from where his son, Charlton Truluck, was celebrating his birthday at his grandparents' house, per the outlet.

When the family later heard a "boom," they assumed it was thunder, Adrian Truluck told NBC News.

"We were thinking it was rolling thunder and didn't give it another thought until we saw the plane was missing," she said.

But when news emerged on Monday that an advanced F-35 fighter jet had gone missing on Sunday during a training mishap, the family realized the plane they saw was likely the lost aircraft, NBC News reported.

The pilot had ejected from the aircraft, and it's suspected to have kept flying in autopilot mode. On Monday, debris from the jet was found about 80 miles away from where the pilot exited the aircraft.

Meanwhile, another Williamsburg County resident's description of how he heard the F-35 crash has gone viral.

"I heard a screeching. Between a screech and a whistle," Randolph White told local channel WCBD, before demonstrating the screech himself.

"I said, 'What in the world is this?' And I heard a boom!" White added. "And my whole house shook."

The Marine Corps is investigating the incident.

The press service for the Marine Corps did not immediately respond to a request for comment sent outside regular business hours.