LOS ANGELES — Boston gangster James “Whitey” Bulger kept hundreds of thousands of dollars in cash hidden behind the walls of his Santa Monica, Calif., apartment and traveled — sometimes in disguise and armed — to Boston, Las Vegas and Mexico to purchase pharmaceuticals, according to court records made public Monday in Boston.

The documents offer tantalizing additional details about how Bulger and his longtime companion, Catherine Greig, managed to live undetected in Santa Monica for at least 14 years, even though he was one of the FBI’s 10 most wanted fugitives.

The documents said that when FBI agents arrested Bulger last Wednesday, they found $822,198 inside the apartment, “much of it in packages containing $100 bills that were bundled together and hidden inside a wall in the apartment.”

Federal prosecutors wrote that the money allowed Bulger and Greig to have a “relatively comfortable lifestyle.”

FBI agents are quoted in the documents as saying Bulger later admitted traveling from time to time outside the Santa Monica area. “Bulger waived his Miranda rights and admitted that he had been a frequent traveler as a fugitive. Bulger acknowledged visiting Las Vegas on numerous occasions to play the slots and claimed he won more than he lost. Bulger also admitted traveling to San Diego and then crossing over into Tijuana to purchase medicines,” court records say.

Bugler also told the FBI he once traveled to Boston “armed to the teeth” because he “had to take care of some unfinished business.” No further details on that trip were available.

The 81-year-old is allegedly responsible for numerous crimes, including 19 killings, and faces two separate federal indictments, one from 1995 and the other from 1999.