Broken Mask incident

The Broken Mask incident was an massacre that took place in Diamond City in the year 2229.

Background
Sometime during May 2229, a man by the name of Carter entered Diamond City and joined a group of residents at the bar at the center of town. Carter started telling stories and making conversation with the people around him. A large group of people started to crowd around him to listen to his stories. After a few hours and having a few drinks, something in Carter shifted. He had suddenly lost his smile and his cheek started to twitch. Mr. Carter suddenly pulled out a revolver and calmly, without even thinking twice, shot Henry, the bartender, square in the head. Carter continued on his rampage, killing an additional 3 to 4 people before finally being brought down by Diamond City security. Inspection of the corpse revealed that Carter was not an actual human being at all, but was in fact an Institute synth, only more advanced than the previous generations of synths.

This incident came to be known as Broken Mask, and lead to the people of the Commonwealth learning of the existence of 3rd generation synths.

Appearances
The Broken Mask incident is a mentioned only event in Fallout 4