Operation Body Count

"Operation Body Count is a 1994 first-person shooter that used the Wolfenstein 3D ray casting engine. It was developed and published by Capstone Software.
Terrorists have taken over the UN Building and have seized the government officials in the building. They are now being held as hostages in the top floor of the building by Victor, the leader of the terrorist gang.
As a member of a special Government Assault Team, it is up to the player to command their team and reach the top floor (the 40th level), rescue the hostages and eliminate the terrorist threat by killing Victor.
Using a modified Wolfenstein 3D engine, the gameplay is very similar to the majority of other "clones" of the time. The game consisted of 40 levels. The first few levels are set in the sewers, where you attempt to make your way up to the basement of the building.
Upon getting into the UNN building, you then combat the terrorists. When you make it up to level 40, you come face-to-face with Victor himself."

Source: Wikipedia, "[en.wikipedia.org/wiki/Operation_Body_Count Operation Body Count]", available under the CC-BY-SA License.