Head to Test Site Washington to stop Blackwatch's Specimen release. Defeat the Brawler by evading its attacks and landing some quick hits on it. After defeating it, you'll acquire claws, making your melee attack even more damaging.
Specimen is down!
Kill the next brawler to continue. After defeating it, you'll get a bonus objective. Perform a Claw Pounce attack to the enemy soldier to earn bonus EP. Kill the next waves of Blackwatch footsoldiers until you get the prompt to pick up rocket launchers.
Pick one up and destroy the enemy vehicle. Once done, return to the church and talk to Father Guerra to complete the mission.