TUCSON — Television images of the chaotic scene after the Jan. 8 shootings here do not convince them. Neither do the funerals for the deceased, the scars of the wounded or the federal prosecution of the man accused of being the gunman.

Some conspiracy Web sites are claiming that the shootings that nearly killed Representative Gabrielle Giffords and did end the lives of a federal judge, a 9-year-old girl and four others never actually took place. One particularly bizarre site, run by a Texas man, says it was all a government hoax that used actors.

Such obviously fantastic claims would usually not merit the attention of law enforcement, but they have in this instance because some believers have been confronting, and alarming, some of the people associated with the case in recent weeks.

Richard Kastigar, investigative chief of the Pima County Sheriff’s Department, said he passed information about the Web site to his intelligence unit. He reacted angrily to those denying the shootings. “There were bodies sent to the morgue, people’s loved ones,” Mr. Kastigar said.