The event timer will count down, and will only end once it reaches 0, or once the marked vehicle is fully occupied. Once entered, and the timer finished, Merryweather units will begin to spawn around the player's vehicle. At first, they will spawn in other similar vehicles, for example, if the player is in a Buzzard, Merryweather agents will pursue in Buzzards. Eventually, after more agents are killed, they may spawn other modes of transport, such as by air vehicles and land vehicles.
Once all patrols have been killed, Kill List will end. The vehicle the player/team are in will then self destruct in 15 seconds.
The score the team/player gains is the number of successful kills they acquire against Merryweather operatives. Merryweather will spawn in numerous land and air vehicles, including:
The number of targets required to be killed in order to complete the event depends on the vehicle(s) Merryweather spawn in, ranging from 9 targets (9 individual P-996 LAZERs) to 44 targets (11 four-man Buzzard Attack Choppers).
Occupy (or at least attempt to) all seats in the vehicle. The more players, the better the chance of successfully killing all the enemies in a shorter space of time.
If there are only 2 players in an armed vehicle, it is best if the second player occupies a mounted weapon, such as the Buzzard's missile launcher, or the Valkyrie's cannon.
Originally, the Savage towards the end of Kill List in helicopters was only able to use its missiles, however, as of The Doomsday Heist, the helicopter is able to use its standard explosive rounds. These can instantly kill the occupants and severely damage the helicopter - since the Buzzard is significantly more durable during Kill List than in regular gameplay, it can withstand several shots, however it's best to approach the Savage with care and use missiles from a far distance to avoid the Savage's explosive cannon.
If the player is quick enough, before the vehicle is "locked" to prevent players escaping, the player can quickly exit the vehicle before Kill List begins (albeit all other players are already in the vehicle).