SAN FRANCISCO >> A search of the San Francisco apartment of a social media expert turned up ball bearings, screws and components needed to make a homemade bomb, the FBI said in an affidavit unsealed Tuesday.

"FBI bomb technicians believe that the device was designed to maim or kill a human being or human beings," FBI Special Agent Michael Eldridge said in the document.

A circuit board described in the document was designed to serve as a remote control, allowing detonation of the device from afar, Eldridge said.

Investigators said they found the materials inside a bag at Ryan Kelly Chamberlain’s apartment during a search over the weekend. The discovery prompted a nationwide manhunt for the 42-year-old Chamberlain.

The FBI has not said what, if any, specific plans Chamberlain might have had for the device, or how they were alerted to the material.

Chamberlain appeared in federal court after being charged with one count of possession of an illegal destructive device. He was accompanied by a public defender but did not enter a plea. He wore the same shorts and shirt that he had on when he was arrested Monday near the Golden Gate Bridge.

Though Chamberlain was considered armed and dangerous, FBI spokesman Peter Lee said Monday during the manhunt that he did not seem to pose an immediate threat to public safety.

"Anyone who has the means, methods and access to make a bomb should be considered armed and dangerous," Lee said before the arrest.

Police Chief Greg Suhr described Chamberlain as someone who was in crisis and getting "more desperate by the moment." He was arrested by officers who responded to a report of a person matching Chamberlain’s description.

Chamberlain spotted the officers and tried to flee but was taken into custody after a brief chase and struggle, police said.

Morgan Manos, who saw the arrest and captured it on video, told the San Francisco Chronicle that Chamberlain looked surprised and frantic.

He was wearing shorts, a sweatshirt and a beanie hat, Manos said, adding: "They took him down hard."

Multiple agencies, including hazardous materials crews, searched Chamberlain’s apartment on Saturday in the Russian Hill neighborhood, blocking off the street to vehicle and pedestrian traffic for much of the day.

Alex Clemens, a partner of the San Francisco-based Barbary Coast Consulting, said Chamberlain is well known in the city’s political circles and had been a fixture on the campaign trails for more than a decade. His work in the field ended several years ago.

Clemens, who briefly hired Chamberlain for a project in 2009, said people who know Chamberlain are stunned.

"I believe there’s been a failure in his support system. I’m sad for that," Clemens said. "I hope he will reach out to those who will help him."

Chamberlain also worked as an independent contractor for the San Francisco Chronicle during the 2012 NFL season, doing social media to boost coverage for the San Francisco 49ers Insider iPad app, the newspaper said.

In 2011, Chamberlain taught a "Grass Roots Mobilization" course to graduate students in the public affairs program, said Anne-Marie Devine, a spokeswoman for the University of San Francisco. Chamberlain taught for one semester and wasn’t invited to teach another course, she said.

She said she didn’t know why he was let go because hundreds of adjunct professors come and go at the university.

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Associated Press writers Garance Burke and Sudhin Thanawala in San Francisco contributed to this report.