Space Marine - The bomb will blow up the pipe that is blocking your way. When the pipe is gone you will see a couple more shooters along with a couple regular orcs. They will not run forward. So take out the shooters first and then take out the other orcs.

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The bomb will blow up the pipe that is blocking your way.  When the pipe is gone you will see a couple more shooters along with a couple regular orcs.  They will not run forward.  So take out the shooters first and then take out the other orcs.