ANCHORAGE, Alaska — Israel Keyes, in jail for the killing of an Alaska barista, gradually began confessing to investigators that he had killed others: a couple in Vermont, four people in Washington state, someone in New York.

But he was slow to come forward with details, warning investigators he would stop talking if his name was released publicly.

“He was very, very, very sensitive to his reputation, as odd as that sounds,” Anchorage Police Chief Mark Mew said. “We had to keep things extra quiet in order to keep him talking with us.”

Keyes committed suicide in an Alaska jailhouse Sunday, leaving behind an incomplete picture of a loner who traveled the country for more than a decade, picking victims at random and methodically killing them. Officials believe there are more victims in other states, but they may never know who they are.

Authorities wouldn’t say how Keyes killed himself, only that he was alone in his cell. They also did not say whether he left a note.

“We’re going to continue to run down leads and continue our efforts to identify his victims so we can bring some closure to the families,” said Mary Rook, the FBI supervisor in Alaska.

While under arrest in connection with the disappearance of 18-year-old barista Samantha Koenig, Keyes confessed to the deaths of Bill and Lorraine Currier, of Essex, Vt., who disappeared in June 2011, authorities said. Keyes confessed to other killings without identifying the victims or saying where their remains were located.

The FBI said Monday that Keyes is believed to have committed multiple kidnappings and murders across the country between 2001 and his arrest in March, often flying to an airport, then driving hundreds of miles before targeting victims.

In interviews with investigators, Keyes detailed extensive planning, including burying caches of weapons at various points across the United States. The FBI says it recovered weapons and items used to dispose of bodies from hiding places just north of Anchorage and Blakes Falls Reservoir in New York.