Over 100 firefighters battled the blaze and stayed through the night to make sure it didn't reignite because at one point the flames were so tall, they were as high as Eucalyptus trees.
It was a full-fledged fire fight from the get go. Flames quickly ate up the dry vegetation on the San Bruno Mountain.
Crews attacked the fire from above and from the ground. Officials say getting on top of it was crucial.
"This was a challenge of a fire due to topography," Cal Fire Chief Scott Jalbert said. "The fire made a run up hill and the aircraft was really the saving grace to slow it down."
But slowing it down didn't mean knocking it down. That was no easy task. The heat and dry conditions didn't help. That's why there were some voluntary evacuations.
"Very nervous, I just took my evening medicine to lower the blood pressure," resident Edna Dimson said.
Standing by and watching the flames rush along Hillside Boulevard was simply too much for some residents. And so they leaped into action.
They attached as many garden hoses as they could find and started spraying.
"Something had to be done," resident Doug Lucas said. "It's our houses we're protecting! It's our property we're protecting."
They even managed to put out some small flames on their own. But they were glad when the experts arrived.
The fire engulfed 40 acres of the mountain. It came dangerously close to Mills Montessori School. The playground was covered in retardant. Fortunately the school was empty on Saturday.
This was the first large scale fire for some who recently returned from fighting the Rim Fire in Yosemite.
A veteran firefighter told ABC7 News that if this fire had started on Sunday, when it's supposed to be even hotter, it would've been much worse.
No injuries or damage were reported.
The cause of the fire is under investigation.