Handsome, athletic and wiry, this veteran of the Chicago stage entered movies convincingly playing edgy, implacable pursuers but soon seemed just as credible in sports dramas and light comedies. Petersen simmered as the morally ambiguous protagonist of William Friedkin's scalding crime drama, "To Live and Die in L.A." (1985). Sporting alarmingly tight pants and a bad attitude, he was a Secret Service agent who lavishly breaks the law to snare a master counterfeiter (Willem Dafoe). The following year, Petersen brought a nearly palpable confusion and anxiety to his portrait of a burned out FBI