The San Francisco media consultant at the center of a FBI manhunt for allegedly possessing explosive materials is no longer considered an "immediate threat," two sources told NBC News Monday, hours after an apparent suicide note and Twitter posting from the man's account appeared online. Jodi Hernandez reports. 
 
 The San Francisco media consultant at the center of a national FBI manhunt has been arrested, FBI officials tell NBC Bay Area. 
 
 The FBI had been looking for Ryan Kelly Chamberlain II, 42, since Saturday, when sources said FBI officials discovered explosives and a chemical that can be deadly in his Russian Hill apartment on Polk Street. 
 
 San Francisco police and FBI agents at about 6:40 p.m. were approaching Chamberlain's car at Crissy Field to make sure no explosives were in the vehicle. 
 
 FBI officials confirmed a "credible sighting" of Chamberlain at about 4 p.m. at the Mad Dog in the Fog bar in San Francisco's Haight district. A person spotted Chamberlain and called 911, according to the FBI. 
 
 Agents responded to the area and were conducting interviews late Monday afternoon. 
 
 Chamberlain was is no longer considered an "immediate threat," two sources told NBC News Monday, hours after an apparent suicide note and a tweet from the man's accounts appeared online. 
 
 Two sources familiar with the investigation told NBC News on Monday that at this point, they don’t believe that Chamberlain, a social media expert and well-known political consultant, presents an immediate threat to public safety. Officials had earlier called him "armed and dangerous." 
 
 A message posted Monday to a Twitter account carrying Chamberlain's name said "nothing they're reporting is true." 
 
 A panicked update to my letter that should have posted by now. Nothing they're reporting is true. No "stashes." Not "armed and... — Ryan Chamberlain (@poliholic) June 2, 2014 
 
 An apparent suicide note titled “Goodbye” was also posted to an iCloud account. The source of both messages could not be independently verified by NBC Bay Area, and the FBI declined to comment on the three-page letter, timed to go out on Monday through the social media management system Hootsuite. 
 
 Chamberlain is a social media expert and a well-known political consultant. 
 
 Various media outlets, including SF Weekly, reported that the note was sent out on Facebook. But by noon on Monday, that note was not on Chamberlain's Facebook page, though several posters were referencing it and sending out the iCloud link. 
 
 The note discusses Chamberlain's depression, his mother, whom it calls a "religious addict," and a time in 2003 when he was "left out" of getting any credit for helping California's Lt. Gov. Gavin Newsom win his San Francisco mayoral seat in 2003. 
 
 The letter also discussed his two needs in life: "A person and a purpose." "All I ever wanted was someone to be madly in love with," the letter states. "Everyone wants that. Lots of people get it. But it always eluded me." 
 
 The letter says that if anyone was reading the note, which he said was posted on Hootsuite delay, "that means we probably don't know each other anymore, and I owe everyone an explanation." 
 
 The two sources told NBC News that the FBI, taking an abundance of caution, issued a nationwide alert to federal, state and local law enforcement to make sure officers are aware of and take a "defensive posture" in dealing with Chamberlain, given the explosive materials recovered from his home Saturday. 
 
 In addition, the sources told NBC News that Chamberlain has family in multiple states so they wanted to cast a broad net. The bet is that he is likely still in Northern California. 
 
 FBI spokesman Peter Lee said Sunday, in an effort to dispel some rumors, that agents had not found any ricin or other chemical or biological threats in the home. "He did possess explosives at his residence," however, Lee added. 
 
 Chamberlain is 6'3" tall, weighs 225 pounds and has blue eyes and brown hair, according to Lee. He was last seen south of San Francisco Sunday, driving a white 2008 Nissan Altima with a California or Texas license plates of either 7FQY085 or BX9M042. The FBI also provided a photo of him. 
 
 Mark Mosher, creative director of San Francisco consulting firm BMWL, said Chamberlain had been hired by almost every local political consulting firm at one point or another. He has known Chamberlain through years of working on various campaigns together. 
 
 "I think for somebody to post publicly that this is a misunderstanding," Mosher said. "They ought to give him room to try to turn himself in and work it out." 
 
 During the 2012 NFL season, Chamberlain was an independent contractor for the San Francisco Chronicle and tweeted and posted links to Facebook to boost coverage for the San Francisco 49ers Insider iPad app, according to the Chronicle. 
 
 Most recently, he worked in public relations for several Bay Area tech, apparel and marketing companies. 
 
 Chamberlain, a Bay Area native, attended Iowa State University before embarking on a career as a music journalist in Des Moines, according to his online resume. He later moved to San Francisco, and at age 30, he made a bid for a spot on the Republican Party County Central Committee in San Francisco, an organization that governs the local party and doles out critical endorsements. 
 
 The past chair of the San Francisco Republican Party, Howard Epstein, told NBC Bay Area, however, that Chamberlain had switched parties and become a Democrat. 
 
 Epstein said he was absolutely stunned at the news surrounding Chamberlain. 
 
 “To have the explosives and all that is just totally mind-boggling to me,” Epstein said. “I’m hoping that he turns himself in. I hope he doesn’t get into any more trouble. I don’t know what he’s thinking. I don’t know what he’s been doing the last few years, what’s going on in his head. I’m just hoping that this all comes out and nobody gets hurt.” 
 
 NBC News' Andrew Blankstein and NBC Bay Area's Diane Dwyer, Riya Bhatterjee, Vince Cestone and Kimberly Tere contributed to this report. 

 Ryan Chamberlain, the San Francisco media consultant who became the focus of a manhunt after agents allegedly found explosives in his apartment, was arrested near Crissy Field on Monday evening, the FBI said. 
 
 Chamberlain was taken to a police station and booked on suspicion of possessing explosives in violation of federal law, said a law enforcement source who asked not to be identified. 
 
 A police bomb squad, meanwhile, used a robot mechanism to search his car. 
 
 According to the law enforcement source, police on patrol had spotted Chamberlain’s white four-door sedan parked outside the Beach Hut Cafe, in view of the Golden Gate Bridge, at 6:22 p.m. 
 
 Hours earlier, Chamberlain posted an apparent suicide note on his Facebook page and the FBI responded to a possible sighting at a Lower Haight bar. 
 
 At the scene of the arrest, a witness reported seeing police and federal agents detain Chamberlain outside the cafe. “He looked pretty surprised and frantic. He was asking for help,” said Morgan Manos, an Uber driver who recognized Chamberlain. “He saw me recording (with a video camera) and asked me for help.” 
 
 Manos said Chamberlain was wearing shorts, a sweatshirt and a beanie and looked scared. “They took him down hard,” Manos said. 
 
 The law enforcement source said Chamberlain got out of the car and was arrested without incident, although Manos’ video showed Chamberlain struggling as officers took him to the ground. 
 
 Here is Manos’ video of the arrest, via KGO-TV: 
 
 And here’s another view of the arrest, courtesy of Phillip Hirsch: 
 
 Tweets from Chronicle staff members and others on the arrest: 

 Ryan Chamberlain has posted an update from his social media accounts. "A panicked update to my letter that should have posted by now. Nothing they're reporting is true. No 'stashes.' Not 'armed and dangerous.' No 'car rigged to explode.' I explored some ugly websites, a year-ish ago," he writes. 
 
 A panicked update to my letter that should have posted by now. Nothing they're reporting is true. No "stashes." Not "armed and... — Ryan Chamberlain (@poliholic) June 2, 2014 
 
 Ryan Chamberlain, a 42-year-old San Francisco man who is sought by authorities after an FBI raid of his apartment on Saturday allegedly revealed explosives, appears to have posted a goodbye note on iCloud. 
 
 An iCloud user with the username Ryan Chamberlain writes that the letter was posted on a Hootsuite delay, "and now it's live, which means I wasn't around to stop it from posting." 
 
 In the letter, the iCloud user writes about experiencing depression after struggling with political campaigns and relationships. Chamberlain is a political consultant. 
 
 Recently, the writer states, "I explored myriad ways I could put an end to what I was going through. I binge-watched dark TV, sometimes didn't get off the couch for days, and scoured the Internet absorbing fuel for morbid fantasies. Some of that activity seemed to attracted the attention of some visitors today...who have made it rather evident that this is the end of the line for me." 
 
 Neither the FBI nor Chamberlain returned requests for comment about the authenticity of the letter. 
 
 Those who worked with Chamberlain were shocked to learn he is the subject of a major FBI manhunt. 
 
 San Francisco Board of Education Vice President Emily Murase, who hired Chamberlain to be her campaign manager when she unsuccessfully ran for the board in 2008, said there was nothing unusual about his behavior. 
 
 “He was perfectly professional,” Murase said. “He spoke with volunteers and did outreach, [what a] normal campaign manager would do.” 
 
 Chamberlain was referred to Murase by campaign consultants after he reportedly worked on Lt. Gov. Gavin Newsom’s then-mayoral campaign, she said. 
 
 The last time she heard from Chamberlain was in 2010, when he wrote her an email congratulating her on winning a seat on the Board of Education. Murase said she used a different campaign manager for that election in part because Chamberlain wasn’t available, but not because she was unhappy with his work. 
 
 “I was a first-time candidate so I had no point of reference, [but] he worked hard and I had no real issues,” Murase said. 
 
 Like others, Murase was saddened and surprised when she heard of the FBI search for Chamberlain. 
 
 “I was just shocked and speechless,” she said. “It’s a terrible situation.” 
 
 Ryan Chamberlain letter
– After a nationwide manhunt, the FBI says the San Francisco social media expert and political consultant suspected of stockpiling explosives was captured within sight of the Golden Gate Bridge. When agents arrested Ryan Kelly Chamberlain II at a cafe, he "looked pretty surprised and frantic," a witness tells the San Francisco Chronicle. "He was asking for help." Before the arrest, an apparent suicide note was posted online, which Chamberlain had apparently written soon after his apartment was searched on Saturday and timed to go out yesterday. After experiencing depression, "I binge-watched dark TV, sometimes didn't get off the couch for days, and scoured the Internet absorbing fuel for morbid fantasies," the note says, per the San Francisco Examiner. "Some of that activity seemed to attracted the attention of some visitors today ... who have made it rather evident that this is the end of the line for me." Another posting, apparently also timed to go out on a delay, said, "Nothing they're reporting is true. No 'stashes.' Not 'armed and dangerous.' No 'car rigged to explode.'" Sources tell NBC that by the time of his arrest, Chamberlain was no longer considered a threat to public safety.