"That's when the car exploded and we saw just a huge mushroom cloud of flames," Steinwand said in an exclusive interview with NBC San Diego.
The flames were coming from the mangled wreckage of three vehicles involved in a head on collision on August 9.
It happened when a Ford Expedition, driven by 17-year-old Natalie Nield of Carlsbad, crossed into oncoming lanes, slamming into a van and a Subaru.
"That's when he (Williamson) jumped out of the car before I was completely stopped and took off running," Steinwand said.
Williamson, a volunteer firefighter for the Bishop Fire Department, had seen bad wrecks in his 25 years of service.
"But I've never seen anything like this," Williamson said. "I started looking around, I saw several people on fire."
Two San Diegans, 19-year-old Derek Thomas and 22-year-old Drew Delis, were in the Expedition when it crashed. They were lying near the vehicle with flames coming from their clothing.
Deputy sheriff Shane Scott was already there helping people. He happens to be one Williamson’s closest friends.
The two men started pulling the victims from the flaming wreckage.
"I drug Drew first to Amy and then I went back to Drew and drug him as far as I could, and Shane helped me drag him back to Amy," Williamson said.
Badly burned but still alive, Derek and Drew were able to talk as Steinwand helped them.
"They wanted me to call their parents and tell them they were in a crash but they were okay," Steinwand said.
Other drivers stopped to help and brought towels and water to Steinwand.
"I kept soaking the towels and pouring the water on both boys because they kept asking me to help them because they still thought they were on fire," Steinwand said.
Derek asked Amy if his girlfriend Amanda Post, 18, was okay. She was still inside the burning Expedition.
"I knew where she was, but I told him that I didn't know and I was just taking care of him," Steinwand said with tears in her eyes.
She knew Amanda didn't make it and neither did Natalie.
"That was tough," Steinwand said.
But Derek and Drew survived, thanks to two strangers who cared enough to pull over and risk their lives to help others.
"I don't consider myself a hero," Amy said. "I just hope somebody would do the same thing for my kids."
"It was just nice to know that I was able to give life back to some parents," John said.
On Saturday, the two are meeting with Drew's parents. They invited Williamson and Steinwand to San Diego so they could personally thank them for saving Drew's life.