Angered by her reluctance, the rich shaman called upon other equally strong shamuses to punish her.
There doesn't appear to be an etymological connection between the words, and the origin of "shamus" itself is uncertain: it originally referred to police, and is likely some cross-fertilisation of Yiddish shammes (a beadle or sexton in a synagogue) and the Irish personal name Séamus (historically, many New York police were of Irish stock). But idly Googling led me to a different connection via Not Remotely Controlled: Notes on Television (Lee Siegel, Westview Press, 2007, ISBN 0465078109) - a scholarly analysis of US television whose chapter on Monk finds close analogies:
Monk, for those who haven't seen the programme, is a deeply neurotic detective who, following a psychological crisis after the murder of his wife, suffers from a variety of phobias and compulsions. These, paradoxically, aid him in his work ("It’s a gift ... and a curse"). Siegel's analysis notes the similarity to the psychology of shamans, who typically suffer "shamanic illness" of a recognisably psychological flavour, and begin their career after a particular initiatory crisis: see Is the Shaman Sane? in Shamanic Worlds: Rituals and Lore of Siberia and Central Asia (Marjorie Mandelstam Balzer, M.E. Sharpe, 1997, ISBN 1563249731).
It wouldn't be hard to extend this analogy to other fictional detectives: for instance, Sherlock Holmes, with his intense concentration, mood swings and ragged nerves (not to mention drug use, another common feature of shamanic ritual). In this vein, Dysthymic Dicks (On the Melancholic Shamus, from Dupin to Cracker) by Harvey Roy Greenberg, Clinical Professor of Psychiatry, offers a tour of the many psychologically troubled fictional detectives. While he doesn't mention shamans directly, his description of such detectives as "wounded healer" is a phrase classically applied to shamans. Greenberg's site The Movies on Your Mind is well worth exploring for its interesting takes on media critique from a psychoanalytic perspective.
Addendum: 16th February 2009. Having slept on the idea, a few other examples of shamanic fictional detectives surfaced. In Randall and Hopkirk (Deceased), Randall achieves his results by, like shamans, communicating with a guiding spirit. There's Colin Dexter's Inspector Morse, in which Morse gains some of his powers by contemplation in a drug-altered mental state (he believes beer is an aid to thought) and has a distinctly shamanic motif of a hidden true name that relates to his spiritual origins ("Endeavour", a name from the same Quaker roots that gave him his sense of duty). And there's the reinvented Inspector Abberline in the film version of From Hell, who gains insights from clairvoyance under the influence of absinthe and opium.
Addendum: 23rd February 2009. I just ran into a further example, the Sonny Baca series of novels by the acclaimed Mexican-American author Rudolfo Anaya (Zia Summer (1995), Rio Grande Fall (1996), Shaman Winter (1999), and Jemez Spring) in which the New Mexico private detective hero literally becomes a shaman.
Addendum 2: March 6 2009. Detail promoted from Comments: Dr C just drew my attention to another example of the crossover, Tony Hillerman's Leaphorn and Chee novels. See Tony Hillerman's Jim Chee and Joe Leaphorn Mysteries.