Friends and family members of the truck driver, identified as 68-year-old Joe Bartowski, said they believe he did everything in his power to steer clear of other cars on the road.
The crash happened about 2 a.m. when Bartowski came upon another crash scene and swerved to avoid the cars.
The tanker rolled and caught fire, sending a huge plume of smoke and flames into the air. Officials with the Washington Department of Ecology said the tanker being hauled by Bartowski was carrying 9,000 gallons of fuel.
"Joe Bartowski was a wonderful man. He had a heart of gold," said Nancy Buckus, a close friend of Bartowski.
She said the Sumner man got into trucking a few years ago to better provide for himself and his wife.
"He just enjoyed the freedom of being on the road," Buckus said.
State troopers said Bartowski's truck was forced off the road by a crash caused by a man who lost control of his car in the southbound lanes of I-5.
Investigators believe the driver of that car, 21-year-old Stephen Palmer, may have been under the influence of drugs or alcohol.
Palmer, who has a history of speeding, was arrested and booked into the King County Jail for investigation of vehicular homicide.
Buckus said Bartowski often talked about the potential dangers of his job.
"Joe used to talk about some of the crazy drivers that he would see and would tell us, make sure if you're ever going to pull in front of a semi truck, give them plenty of room. They're so big they cant stop quickly," she said.
"I absolutely know in my heart and will always know that Joe did everything in his power to ensure that no one else was harmed."