Massacre of the Prydwyn

The Massacre
The Massacre of the Prydwen occurred in 2288~, after Proctor Teagan asked General Dave to betray the Minutemen and plunder one of his own settlements. In a fit of rye whiskey-fueled rage, General Dave gunned down Proctor Teagan, which started a firefight with the Brotherhood Of Steel aboard the Prydwen. When the shooting stopped, General Dave stood victorious. With every Brotherhood member on the Prydwen dead, General Dave plundered the bodies of their gear, most notably Maxson's Battlecoat and the Captain's Hat, which he ripped the emblem off and replaced with a Minutemen one.

Exodus to Vault 88
The massacre was the beginning of the end for the brotherhood, after the fall of the Prydwen the survivors of the Minutemen-BOS war fled to the semi-abandoned Vault 88.