ON A MILD SUNDAY last summer, a string of "popping sounds" drifted through the lazy night air of Beverly Hills around 10 o'clock. "I didn't think anything of it," said Tom Zlotow, a neighbor who soon learned that the noises he'd heard from the house right behind his were echoes of the most sensational crime in the history of Beverly Hills. "I didn't even think it could be gunfire, especially around here."