Major story spoilers ahead.
Delta squad then move towards the train station where they had to get aboard an armored freight train that carried the Lightmass Bomb. At the train station the team gets attacked by Locusts which results in only Marcus and Dom getting aboard the train, while Baird and Cole get left out. They both then fight across the train, trying to reach the Lightmass Bomb but encountering lot of Locust resistance, including a Berserker.
At last they manage to reach the Bomb, only to find General RAAM (who killed Kim) guarding it. Marcus and Dom then defeat him. Marcus then uploads the data to the Lightmass bomb and escapes off the train with the help of Dom and Col. Hoffman.
The bomb, along with the train approaches a broken bridge and falls through it into the Imulsion. The Lightmass bomb then gets activated, killing almost everyone inside the Locust tunnels.
At the end of the game, the Locust Queen is heard saying that they have not been defeated yet and they will fight back.

One of the remaining Locusts after the Lightmass Bomb blast


