The Heist Mode is a cut game mode from Counter-Strike: Global Offensive.
Reference to game mode can be found in
func_bomb_target brush entity from CS GO SDK, where in bush properties description says "This is a Bomb Target designed for the Heist game mode."
In the November 28, 2016 update, Adding to game files new terrorist model named "
tm_heavy_riot" currently without textures (all black) it's possible is related to game mode.
- func_bomb_target on Valve developer Wiki