** UPDATE: The nationwide manhunt is over after three days, as police apprehended 42-year-old Ryan Chamberlain under the Golden Gate Bridge in San Francisco. The manhunt started after police raided Chamberlain's apartment and found a stockpile of explosives and bomb-making materials.

Watch video of the arrest above.

A nationwide manhunt is underway for a 42-year-old man suspected of possessing explosive materials. The suspect is Ryan Kelly Chamberlain II, a social media consultant from San Francisco, California. Investigators say he had bomb making materials in his apartment. When they arrived with a search warrant on Saturday, he was gone.

FBI agents say earlier reports that he had the poisonous substance ricin are false, but they are considering him armed and dangerous. An FBI spokesman says Chamberlain was last seen wearing a dark blue hooded sweatshirt and jeans. He’s said to be traveling in a white 2008 Nissan Altima that has Texas or California license plates.

Trace Gallagher reported that the search warrant and affidavit have both been sealed. The San Francisco Examiner has published what appears to be a suicide note by an iCloud user named Ryan Chamberlain. It reads in part, “Betrayal, abandonment, isolation and loneliness. I couldn’t take it this time. … Time’s up. Thank you. I’m sorry. I love you.”

This afternoon, a man named Ryan Chamberlain posted on Twitter: “A panicked update to my letter that should have posted by now. Nothing they’re reporting is true. No ‘stashes.’ Not ‘armed and…”

Gallagher reported that Chamberlain worked on political campaigns in the San Francisco area for both Democrats and Republicans, including former San Francisco Mayor Gavin Newsom. He was also a lecturer at the University of San Francisco for a short time.