"I've heard of burglars in the neighborhood, you just never think it would happen to you," Rachel Hardyck said.
But it did. On Friday morning, burglars ransacked Hardyck's home in the Belmont hills.
"The nice jewelry box where I kept my higher end jewelry items, my real stuff was empty," she said.
Among the items taken was an heirloom ring worth $14,000. The intruders pried open the dead bolted door to get in.
"It was completely busted open, hanging off, just in the middle of the room with the dead bolt sticking out of the door," Hardyck said.
Two other Belmont homes were burglarized on the same day. Neighbor Jill Mannie knows another resident who opened her door when a stranger knocked. She says the man gave her a strange excuse.
Last Friday, Hillsborough police reported door-knock incidents at two homes. In San Mateo, another attempted residential burglary that same day. There were so many door knock burglaries recently that Belmont police produced a public service video to help educate residents.
Security video from an attempted burglary in San Jose show how it can happen. A woman with an infant in her arms walks up to the front door and knocks and rings the doorbell. The homeowner told ABC7 News a nanny was in the house but did not answer because the woman was a stranger. At one point, the woman outside even peered through the window to see if anyone is home. A little while later, two men appear in the back of the house, after jumping a fence from the neighbor's yard. The video shows them trying to pry the sliding glass door from its tracks. They use a metal bar as well as a shovel to loosen the door, but they have no luck. They suddenly dash off, apparently startled by the nanny, who looked out the window.
In Belmont, Police Capt. Pat Halleran says most of the intruders they have arrested come from the East Bay.
"We've seen several suspects coming out of Oakland, San Leandro, Hayward, Alameda County that we hadn't seen before," Halleran said.
Many residents say they plan to install alarms and video cameras.