"She told me, you know, 'My friends are inside,' and so I turned around and the car, it was really bad already. There was fire all over the car," Ganaja told NBC4-TV.
Underwood's mother, Valerie Lucas, told reporters Tuesday that her daughter was saved after Ganaja "heard her screaming and he was able to literally drag her away from the vehicle."
In a statement, she said she was "deeply grateful" to the Hook Burger deliveryman who was there moments after the crash, as well as the first responders and doctors.
The deadly crash shocked many in the community, including longtime police officers, who said it was among the worst they'd seen in years.
The Burbank City Council on Tuesday held a moment of silence for the victims, with some of their friends and family members in the audience.
An investigation into the cause of the crash remained ongoing, although authorities have said they believe speed may have been a factor.
Katherine Laprell, a former Burroughs student who recently saw one of the victims, told the Burbank Leader she was still in shock over the news days after the crash.
"People need to be more careful – I really hope this is a wake-up call for everybody," Laprell said. "I've never had a tragic loss like this happen."
A vigil at the crash site grew quickly over the last few days as friends stopped to remember the victims and share their grief.
Ganaja, connected to the tragedy by its immediate aftermath, also offered his condolences to the victims' families and friends.
"I feel so bad for them," he told NBC4.