Backfiring sheriff's bus routinely startles San Bruno residents

SAN BRUNO, Calif. - A startling sound has been repeatedly scaring some neighbors in San Bruno, and after months of mystery, it has been traced to a backfiring bus belonging to the San Francisco Sheriff’s Office.

Surveillance videos over several weeks show the bus traveling down Moreland Drive and backfiring while transporting prisoners from the county jail to the courthouse in downtown San Francisco.

"I thought it was our water heater blowing up the first time I heard it," said resident Marie Ryder. "It’s that loud and that shocking."

Residents said on Thursday the surprise exploding sound typically occurs between 6:30 and 7:30 in the morning.

"Nice and peaceful out and people going to work and all of a sudden you hear a boom!" said resident Robert Jenkins. "It shakes the house."

Initially, those who live near the jail were not sure what was causing the loud, constant bangs. Residents said they’ll sometimes hear more than one explosion within seconds.

"It’s just random every other day," resident Selina said. "It startles my little dog."

In the last few weeks, the sounds were captured on cameras mounted outside homes. The sheriff’s bus is seen time after time backfiring.

"I want to see it stop," said Jenkins. "This is ridiculous. There’s something wrong with the bus."

A spokesperson for the San Francisco Sheriff’s Office told KTVU the old bus has been in for repairs before but the loud problem persists.

"Our aging fleet, responsible for transporting custodies to court, has not see the addition of new vehicles in four years," the sheriff’s office said in a statement. "We have requested funding for new vehicles over the past two years to transport our population safely, but unfortunately, our requests have been denied."

After KTVU started asking questions, the sheriff’s office said the bus has temporarily been removed from service as a courtesy to residents.

Brooks Jarosz is an investigative reporter for KTVU. Email him at brooks.jarosz@fox.com and follow him on Facebook and X @BrooksKTVU