Mercer

Captain Mercer is a member of the Minutemen in the Fallout 4 Creation Club content "Gunners vs. Minutemen."

Background
An old friend of Colonel Ezra Hollis, Captain Mercer was a Minuteman officer who lost everything following the Quincy Massacre, and together with his men were some of the last who still believed in the ideals of the Minutemen. Reasoning that the Gunners had taken their family, their friends, and their homes, his unit decided to mount a last suicidal mission to try and plant the Minuteman flag in the town square, just to show the Commonwealth they were still there. He knew they stood little chance of succeeding, but having nothing left meant they had nothing left to lose.

Other interactions
Depending on whether one sides with the Minutemen or the Gunners in War Paint, he'll either be found dead on the scene or has to be defeated to complete the quest.

Appearances
Captain Mercer appears only in the Fallout 4 Creation Club content "Gunners vs. Minutemen."