The driver of a car stolen in a violent carjacking is the only survivor after allegedly ramming a motorist and forcing them into the path of a third vehicle, causing a catastrophic high-speed crash that killed three people.

The Bruce Highway north of Brisbane remains closed to all traffic after the three-car collision south of Gympie about 4am on Friday.

The 25-year-old driver of the stolen car was known to Queensland police and taken to hospital with serious head injuries and remains under police guard.

According to police, he was found “in the vicinity” of the ruined stolen vehicle.

It had been stolen in a violent daylight carjacking in Gympie’s main street on Thursday, 12 hours before the highway crash, police said.

An alert for the vehicle was issued after a man armed with a knife threatened a mother and her three children as the family were getting into the Isuzu MU-X.

The terrified mother got her kids out of the vehicle before handing over the car to the robber. She and her children were unharmed.

Police later spotted the stolen car, but the driver refused to stop and escaped.

It was not being pursued at the time of the accident.

The three victims include two women, aged 25 and 38, and a 65-year-old man. All three died at the scene.

Detective Superintendent Ben Fadian described it as a complex investigation and appealed for anyone who saw the stolen Isuzu to contact police.

“We also appeal for anyone who was driving on the Bruce Highway between Federal and Noosa turn-off this morning between 3am and 4am and may have seen that vehicle to please contact Crimestoppers,” Superintendent Fadian said.

“The tragedy is that there are three people now deceased and the ripple effect that has on their families.”

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Queensland Ambulance Service’s Sunshine Coast acting director Nigel Jones said it was a challenging event for all emergency services.

“The scene was obviously quite confronting given the mechanism of the forces involved – it was clearly a very high-speed incident involving those vehicles,” Mr Jones said.

“So much so that our paramedics report that the two patients were killed on impact, with a third patient, unfortunately, passing away shortly afterwards.”

Southbound lanes of the Bruce Highway were expected to be closed for an extended period into Friday. Diversions are in place.

The forensic crash unit is investigating, and no charges have been laid.

– AAP