The wealthy suburb of Phoenix drowses in the heat of the Sonoran Desert, sprinkled with luxury resorts catering to snowbirds in what Arizonans call the Valley of the Sun. June 29, 1978, likely began as nearly all Scottsdale summer days do — temperatures soared above 100 degrees by high noon, and well-heeled residents took refuge in their heavily air-conditioned villas, leaving the wide streets as empty as any Southwest ghost town. It didn’t end that way.