Late on a Saturday night two weeks ago, an unemployed carpenter packed his mother's Toyota Tundra with guns and set off for San Francisco with a plan to kill progressives.

When California Highway Patrol officers stopped him on an interstate in Oakland for driving erratically, Byron Williams, wearing body armor, fired at police with a 9mm handgun, a shotgun and a .308-caliber rifle with armor-piercing bullets, Oakland police say. Shot and captured after injuring two officers, Williams, on parole for bank robbery, told investigators that he wanted "to start a revolution" by "killing people of importance at the Tides Foundation and the ACLU," according to a police affidavit. His mother, Janice, told the San Francisco Chronicle that her son had been watching television news and was upset by "the way Congress was railroading through all these left-wing agenda items."

But what television news show could have directed the troubled man's ire toward the obscure Tides Foundation, which sounds as if it's dedicated to oceanography, or perhaps laundry detergent, but which is in fact a nonprofit that claims to support "sustainability, better education, solutions to the AIDS epidemic and human rights"?

A week after the incident, the mystery was solved. "Tides was one of the hardest things that we ever tried to explain, and everyone told us that we couldn't," Fox News host Glenn Beck told his radio listeners on Monday. "The reason why the blackboard" -- the prop Beck uses on his TV show to trace conspiracies -- "really became what the blackboard is, is because I was trying to explain Tides and how all of this worked." Beck accuses Tides of seeking to seize power and destroy capitalism, and he suggests that a full range of his enemies on the left all have "ties to the Tides Center." On Monday, he savored the fact that "no one knew what Tides was until the blackboard."

For good measure, Beck went after Tides again on Fox that night. And Tuesday night, Wednesday night and Thursday night. That's on top of 29 other mentions of Tides on Beck's Fox show over the past 18 months (two in the week before the shootout) according to a tally by the liberal press watchdog Media Matters. Other than two mentions of Tides on the show of Beck's Fox colleague Sean Hannity, Media Matters said it was unable to find any other mention of Tides on any news broadcast by any network over that same period. Beck declined comment.

It's not fair to blame Beck for violence committed by people who watch his show. Yet Williams isn't the only such character with a seeming affinity for the Fox News host. In April 2009, a man allegedly armed with an AK-47, a .22-caliber rifle and a handgun was charged with killing three cops in Pittsburgh. The Anti-Defamation League reported that the accused killer had, as part of a pattern of activities involving far-right conspiracy theories, posted a link on a neo-Nazi Web site to a video of Beck talking about the possibility that the Federal Emergency Management Agency was operating concentration camps in Wyoming. The killings came after Beck told Fox viewers that he "can't debunk" the notion that FEMA was operating such camps -- but before he finally acknowledged that the conspiracy wasn't real.

Beck has at times spoken against violence, but he more often forecasts it, warning that "it is only a matter of time before an actual crazy person really does something stupid." Most every broadcast has some violent imagery: "The clock is ticking. . . . The war is just beginning. . . . Shoot me in the head if you try to change our government. . . . You have to be prepared to take rocks to the head. . . . The other side is attacking. . . . There is a coup going on. . . . Grab a torch! . . . Drive a stake through the heart of the bloodsuckers. . . . They are taking you to a place to be slaughtered. . . . They are putting a gun to America's head. . . . Hold these people responsible."

Beck has prophesied darkly to his millions of followers that we are reaching "a point where the people will have exhausted all their options. When that happens, look out." One night on Fox, discussing the case of a man who killed 10 people, Beck suggested such things were inevitable. "If you're a conservative, you are called a racist, you want to starve children," he said. "And every time they do speak out, they are shut down by political correctness. How do you not have those people turn into that guy?"

Here's one idea: Stop encouraging them.

danamilbank@washpost.com