BOSTON — The inmates who killed James (Whitey) Bulger, Boston’s notorious crime boss, deliberately moved out of view of surveillance cameras in a West Virginia prison before pummeling him with a padlock that was stuffed inside a sock, law enforcement officials said on Wednesday, as investigations began into how such a murder could have taken place in a supposedly secure facility.

Despite the attackers’ efforts to hide, officials said, cameras caught video images of at least two inmates rolling Mr. Bulger, 89, who was in a wheelchair, into a corner where the attack took place. Mr. Bulger was bleeding profusely when he was found by prison authorities at 8:20 Tuesday morning. Guards immediately undertook lifesaving measures, officials said, but he was pronounced dead.

A prison official identified one of the suspects as Fotios (Freddy) Geas, 51, a Mafia hit man from West Springfield, Mass. He is serving a life sentence at the Hazelton penitentiary in West Virginia for the 2003 killing of the leader of the Genovese crime family in Springfield.

Daniel D. Kelly, who has represented Mr. Geas for many years, said in an interview that he had no idea whether his client was involved in killing Mr. Bulger, who was an informant for the F.B.I., a relationship he manipulated as a cover while he betrayed and murdered rival gang members.