He didn't want to reveal his identity, but the man who called himself "Ivan" has a familiar story.
"I was out for only an hour. When I came back my window was open and my iPads were gone," he said.
He had never been burglarized until last week, "Ivan" said. After calling police, he learned that he was one of several recent victims in Diamond Bar.
"It kind of surprised me, because the officer told me it happened twice in a week," he said.
Diamond Bar seemed to be the quintissential target, police said.
"Criminals will look to expose areas where there is some affluence, where they are going to be successful or profitable," said Lt. Steven Katz of the Los Angeles County Sheriff's Department Diamond Bar office.
While there has been no overall increase in residential burglaries, Katz said the Sheriff's Department has kept a close eye on this city of nearly 60,000.
The average household income in Diamond Bar is more than $103,000, according to the city's website. There have been 17 burglaries in Diamond Bar since the start of 2012, and many may follow a similar pattern dubbed "knock knock" burglaries.
Would-be assailants knock to see if anyone is home and if there is no answer, they break in. The Sheriff's Department patrols here regularly, but said residents are another line of defense.
"Get to know your neighbors," Katz said. "Your neighbors are going to be the folks who are going to know what's out of place in your neighborhood."
One resident said he has made it a point to do just that.
"We have seven or eight gardeners on site," said John Rowe, who has lived in Diamond Bar for 25 years. "I know those folks."
"I just watch for people who look like they don't belong," Rowe said. "Vehicles that look like they don't belong."
Diamond Bar's easy access to freeways may also contribute to the problem, deputies said. Easy in, easy out.
Residents should make the exterior of their homes look less like a target, lock their doors and windows, lock down their safes or conceal valuables in unpredictable places, Katz said.