The first four police cars that roared by with full lights & siren blaring were a hint.
The two fire trucks doing the same indicated that the game was afoot.
The ambulance meant that it was serious.
But when the LAPD helicopter starts orbiting at 500 feet, NOW IT’S A PARTY!!
(Never did figure out exactly what was going on, but it was about two blocks away. The chopper was gone in about five minutes.)