Authorities in San Francisco on Tuesday were looking for suspects who flipped four Smart cars. The small two-seat cars were flipped on their sides or roofs in an apparent vandalism spree Monday in two San Francisco neighborhoods. Police said they didn’t know whether the incidents were a prank or another episode in escalating tensions among some residents who blame the tech industry for rising rents and cost of living. "It’s hard to determine a motive without any suspects identified or in custody," said Officer Gordon Shyy, a police spokesman who said the culprits would face felony vandalism charges.