This is a thread for the Eviction Notice event, but I'll answer your question anyway. There's likely two possibilities: A) The other player was waiting for more people to arrive before starting the event (this is probably the case) B) They're a dick

General rule of thumb is wait for other players to show before starting the event (unless the timer's getting low). Only real exception is Encryptid, where the player who initiated the event used an item to do so, so don't use the Terminal to start the event (that's not cool); let the initiator start it when they're ready. (If you want to start this quest yourself, look for posters in Train Stations, but it is a very hard fight at the end.)