According to the log entries recorded by the anonymous leader of a raider gang, Boppo proposed that the gang established a base at Springvale Elementary School. Later, Boppo attempted an ill-conceived raid on the nearby settlement of Megaton, in which he was killed by sheriff Lucas Simms.
The raider leader laments later, after attempts at digging a tunnel into Vault 101 had met unexpected resistance from giant ants, that if they didn't succeed, he would suffer the same fate as Boppo. Only that this time, the bullets would be coming not from the sheriff, but from their own men.
Boppo is only mentioned in Fallout 3.