NAPLES, FL: Senior executives at Health Management Associates were tired of standing by as HMA shares dropped for no apparent reason.

The slide began on November 1, when news hit that FBI agents had raided the Redding Medical Center in Redding, CA, a hospital run by one of its major competitors, Tenet Healthcare, where two cardiologists stand accused of performing unnecessary surgeries. Investors decided it was time to sell their shares first and ask questions later.

The selling gathered pace after further ...