Christian Deaton, 52, and his wife Michelle Deaton, 48, both of Portland, Oregon, died Tuesday at about 11 a.m.
The investigation continues to determine an official cause of death.
However, a preliminary investigation found that the two bicyclists and the truck were all going north on the roadway when the load of lumber shifted on the flatbed and struck the bicyclists, said CHP Officer Vince Pompliano.
The truck driver, a 55-year-old man from Vallejo, stayed at the scene and cooperated with investigators, Pompliano said.
The couple worked for Nike or its parent company and were avid cyclists and travelers, friends said.
"We have an enormous void to fill in our hearts right now. The impressions they left on us are everlasting," said longtime friend Josh Ring who described the pair as "very skilled athletes."
Ring said, "Cycling is their major love. Traveling a second love."
The couple also enjoyed attending concerts featuring popular 80s and ’90s groups, including Tears for Fears, Pearl Jam and Metallica, Ring said.
Ring said the couple didn't have any children, but were like second parents to his kids.
"I'm speechless right now. There are not many words that can derive a situation we're in. We're left wondering why," he said.
Ring said he finds some solace knowing that died doing something they loved.
"We're not angry, but we're comforted that they went together. And we believe they're in a better place in heaven right now," he said.
Another friend, Nate Retzlaff said, "Christian and Michelle were the most inspirational couple we knew. Humble, generous, thoughtful, loving and hardworking, together they were redefining what it meant to thrive in every aspect of life. I knew Christian for over 25 years, and they were our best friends. They loved our kids like they were their own and blessed our family and friends immensely. I’ve never laughed harder with anyone else as they were so fun and lived life to the fullest. So many are heartbroken today as people like the Deatons come around once in a lifetime."
The truck driver declined to comment Wednesday to KTVU.
In a statement, Central Valley Builders, the company that owns the truck said, "We are devastated by this news, and our deepest sympathies are with the victims' families and loved ones. Central Valley is continuing to gather the facts to determine exactly what happened, including working closely with local law enforcement as they investigate this incident."
Henry Lee is a KTVU crime reporter. E-mail Henry at Henry.Lee@fox.com and follow him on Twitter @henrykleeKTVU and www.facebook.com/henrykleefan