The couple, along with their son and two other men, were returning from a camping trip when their Dodge Neon drifted across the westbound lanes and hit the guardrail at milepost 34 around 6:45 a.m., said Washington State Patrol.

Troopers said the crushing impact threw the car back across the lanes of traffic, sending the occupants’ belongings flying from the car. The mangled wreckage stopped on the opposite shoulder.

“It seems like the driver just fell asleep and drifted off to the left shoulder and struck the guardrail, then struck the actual cement bridge abutment,” said Trooper Cliff Pratt.

The driver of the car, 30-year-old Sean Mitchell, and his wife, 26-year-old Lindsey Mitchell, both died at the scene.

Lindsey Mitchell was sitting in the backseat behind her husband with their 4-year-old son, Cameron, and their 15-year-old nephew, Austin Waage. A family friend, 20-year-old Rick Rigney, was sitting in the front seat.

They told troopers they were returning from a weekend camping trip at Banks Lake in eastern Washington.

Investigators said everyone in the car was wearing seatbelts, including the husband and wife.

“No amount of seatbelts, airbags, or any other type of safety device would have helped these people with the high-energy impact they had with an immovable object,” said Pratt.

The injured passengers were all taken to Harborview Medical Center.

Waage suffered moderate to severe leg and internal injuries and remains in serious condition, police said.

Cameron remains hospitalized in satisfactory condition. Rigney also had minor injuries, but has been released from the hospital.

The crash has closed westbound I-90 at the crash scene for more than three hours. Westbound I-90 reopened at about 10:45 a.m.

Troopers said driving while tired is considered just as negligent as driving drunk.