THIRD STREET — Those who lived in the same Santa Monica apartment building as infamous Boston mob boss James “Whitey” Bulger and his companion Catherine Greig are still finding it hard to believe that the quiet couple known for providing coins for the laundry or giving little gifts was actually in hiding from the FBI.

It’s been a year since Bulger and Greig, who went by the names Charlie and Carol Gasko, were arrested at the Princess Eugenia Apartments on Third Street. The 82-year-old reputed crime boss, who has been accused of 19 murders and eluded law enforcement for more than a dozen years, now sits in a jail cell awaiting trial, while Greig was sentenced earlier this month to an eight-year prison term for helping Bulger.

In Gideon Brower’s radio show “The Couple in 303,” which airs today at 2:30 p.m. on KCRW as part of the UnFictional series and can be found on the station’s website (kcrw.com), the screenwriter who lived across the street from Bulger interviews his neighbors to gain insight into what it was like to live next to a man who stashed dozens of guns and over $800,000 in the walls of his rent-controlled apartment.

From the beginning of the program it is clear that the neighbors can’t seem to come to grips with the fact that the white-haired man and woman they had conversations with were not who they pretended to be. It raises the question, how well do we really know our neighbors?

“I was surprised that some people said that they missed them, and it’s because they miss Charlie and Carol,” Brower said of the subjects of his show. “They still don’t feel like they knew Whitey and Catherine. Those were some other people from Boston. They never saw that side of them and still can’t quite take it in.”

One person interviewed, Josh Bond, summed it up best with this statement: “All I can say is they were very good to me and very kind to me while they lived there … and you know, reconciling that with the fact that he murdered innocent people, I’m not really sure how to understand that. Or if I really need to.”

Brower, who helps produce shows for KCRW’s Warren Olney and volunteers at the Santa Monica College-based station, began working on the radio program — his first — soon after Bulger and Greig were arrested. When he saw the media attention the arrest generated, he felt compelled to document the stories. He found the dichotomy intriguing. Here’s an alleged mass murderer who apparently put the past behind him and tried to start a new life in which he was just an ordinary man who liked to take walks and chat about music. And he lived right across the street, making the experience all the more surreal.

“You see this on TV all the time and it’s always happening to somebody else, so when the threat kind of lands on your own doorstep, it’s just hard to take it in,” he said.

Brower skillfully crafts a compelling, entertaining narrative that draws the listener in and makes them ponder what it would be like to live next to a gangster and whether or not they should inquire more about their neighbors.

“I think most just want to know if their neighbors are a threat to them and I think there’s a pact that you sort of stay out of each other’s way,” Brower said. “You may go one step further and help them out or do favors, but we all want our own privacy. The more we intrude and want to know more about our neighbors’ lives, the more we open up ourselves to that. Some people like that, while others do not.”

It’s not uncommon for people to know little about those who live next door. Some 28 percent of us know none of our neighbors’ names, according to a 2010 Pew survey; it’s particularly pervasive among younger and lower-income people.

Through the Bulger arrest, Brower said he has been able to get to know his neighbors more now that they have something in common to talk about. Having lived across the street from his subjects for many years, Brower was able to get them to open up and reveal more about their time with Bulger, providing details not heard elsewhere. That said, Brower did have some difficulty in getting certain people to go on record, perhaps because of fear for what might happen if they talked.

“He is or was a dangerous guy and people don’t feel comfortable just chatting about it, even though most of what people said about both of them was really positive,” Brower said.

For those who can’t get enough Whitey, “The Couple in 303” is essential. And to those who could care less, the show is sure to have them thinking twice about how much interaction they would like to have with those on their block.

“I think a lot of people would rather observe and invent stories about neighbors then actually find out about them,” Brower said. “That’s kind of more fun sometimes.”

kevinh@smdp.com