The Suicidal Worker is a worker from Spand Express, a shipping company that later shuts down due to destruction caused by Tommy Vercetti.
Events of Grand Theft Auto: Vice City
During the mission Phnom Penh '86 in GTA Vice City, Lance heads to Prawn Island via a helicopter, so Tommy would be able to shoot gang members in aerial mode. During the ride to Prawn Island at one point, Lance passes with the helicopter under the Links Bridge, which connects the two main islands of Vice City. If the player pans the camera backwards to the helicopters' tail as soon as the helicopter passes under the bridge, the player will see a Spand Express worker jump off the bridge and land in the water. The reason this worker committed suicide is maybe due to he has lost his job after the mission Riot.
Some players have speculated that the falling worker could be simply the result of a pedestrian spawn glitch, or perhaps an error in the ped's path. Despite this, it is widely accepted that the Suicidal Worker is just an Easter egg left in the game by Rockstar.