The Great Conflict

You will not stray from your required objective. You ignore the harmless targets evacuating and focus in on the threat in the center of the room. He currently has a holy shield surrounding him and seems to be gathering energy for an offensive ability. You better not give him the chance to use it or you will not survive. You have three options, you may attempt to kill him with your P.E.A.R., use your energy pistol to blow his head off, or attempt melee combat. Which shall it be?