From: MTA10/core/CKeyBinds.cpp
AddGTAControl ( "lalt", "vehicle_fire" );
AddGTAControl ( "mouse1", "vehicle_fire" );
[b] AddGTAControl ( "ctrl", "vehicle_secondary_fire" );[/b]
AddGTAControl ( "num_0", "vehicle_secondary_fire" );
This should work (Server of Client ) side -
toggleControl ( Player, "vehicle_secondary_fire", false)