SANTA MONICA, Calif. – As the FBI chased leads on two continents, Boston mob boss James “Whitey” Bulger spent nearly all of his 16 years on the run in this quiet seaside city, passing himself off as just another elderly retiree, albeit one who kept a .357 Magnum and more than 100 rounds of ammunition in his modest apartment.

Bulger — the FBI’s most-wanted man and a feared underworld figure linked to 19 murders — was captured Wednesday after one of the biggest manhunts in U.S. history. His undoing may have been his impeccably groomed girlfriend.

During a search of Bulger’s apartment after his arrest, agents found $800,000 in cash, more than 30 firearms, including pistols, rifles and shotguns, several types of knives and several pieces of false identification, Steven Martinez, FBI Assistant Director in Charge in Los Angeles, said at a news conference Thursday afternoon.

The weapons were tucked in hiding places throughout the apartment, Martinez said.

Earlier this week, after years of frustration, the FBI put out a series of daytime TV announcements with photos of Bulger’s blond live-in companion, Catherine Greig. The announcements pointed out that Greig was known to frequent beauty salons and have her teeth cleaned once a month.

Two days later, the campaign produced a tip that led agents to the two-bedroom apartment three blocks from the Pacific Ocean where Bulger and Greig lived, authorities said. The FBI would not give any details about the tip.

The 81-year-old boss of South Boston’s vicious Winter Hill Gang was lured outside the building and captured without resistance. Greig, 60, also was arrested.

The arrest of Bulger closed one chapter in a case that had scandalized the FBI. He fled in 1995 after a retired FBI agent who had recruited him as a government informant tipped him off that he was about to be indicted. Soon it was discovered that the Boston FBI had a corrupt relationship with its underworld informants, protecting mob figures for decades and allowing them to commit murders as long as they were supplying useful information.

While Bulger’s capture is the end of a long, frustrating search for the FBI, it could expose the bureau to even more scandal.

One of Bulger’s lieutenants testified in 2002 that Bulger boasted he had corrupted six FBI agents and more than 20 Boston police officers, keeping them loyal by stuffing envelopes with cash at Christmastime.

“If he starts to talk, there will be some unwelcome accountability on the part of a lot of people inside law enforcement,” said retired Massachusetts State Police Maj. Tom Duffy. “Let me put it this way: I wouldn’t want my pension contingent on what he will say at this point.”

On Thursday, more than a dozen FBI agents carried out bags of evidence from the Santa Monica apartment. Authorities said they seized a variety of weapons, including the Magnum, and a large amount of cash.

Retired Massachusetts State Police Col. Tom Foley, who investigated Bulger for decades, said he never believed the various reported Bulger sightings around the world, even the 2002 sighting in London that the FBI said was confirmed. Foley said it was widely believed that the FBI didn’t actively search for the mobster, at least initially.

“Apparently, they should have spent more time in this country looking for him than gallivanting overseas,” Foley said.

On Thursday afternoon, Bulger appeared with his girlfriend in federal court in Los Angeles and was ordered returned to Massachusetts to face charges after he waived his right to a hearing. Balding, with a full white beard and wire-rimmed glasses, Bulger clutched court documents against his chest in court and smiled as he was led away by law officers.

He faces federal charges that include murder, conspiracy to commit murder, narcotics distribution, extortion and money laundering. Greig was charged with harboring a fugitive.

Many people in the Southern California neighborhood where the crime boss lived were not surprised that Bulger could blend in in Santa Monica, a densely populated beachside suburb of Los Angeles where aging, ponytailed hippies, bike-riding environmentalists, Hollywood actors and others regularly rub shoulders with retirees, but usually exchange no more than pleasantries.

“This is the perfect place to hide,” said Maura McCormick, who lives in an apartment building next door. “Nobody bothers anyone here.”

Seth Rosenzweig, a writer who lives down the hall from Bulger’s apartment, said the fugitive, who was partial to baseball caps and dark sunglasses, kept a low profile. He would divert his eyes every time he got into the elevator with other people.

The apartment’s managers said the couple, who went by the names Charles and Carol Gasko, had lived there for 15 years and were ideal tenants who always paid their rent on time and in cash. Santa Monica property records show the apartment had a rent-controlled rate of $1,145 a month.

Catalina Schlank, who has lived in the building for 35 years, said she was friendly with Greig but not so much with Bulger, whom she called a recluse. “They were a handsome couple, but they were kind of mysterious,” she said.

The couple didn’t own a car, choosing to walk everywhere. That’s easy to do in their neighborhood, just down the street from the beach.

The apartment managers also recalled that Bulger seemed concerned for the well-being of others, once giving a building worker his flashlight because he was worried about her crossing the road after she finished her shift at night.