Percival Dumbledore seeks revenge on Ariana's attackers, is imprisoned for it

"And my father went after the bastards that did it, and attacked them. And they locked him up in Azkaban for it."

-- Aberforth Dumbledore (DH28)

After Ariana Dumbledore was attacked and traumatized by three muggle boys, her father Percival went after those boys to seek revenge. The attack was described as “savage” by Elphias Doge (DH2), and was well-publicized. Percival never explained the reason for his attack, in order to protect Ariana, and it was believed to be an anti-muggle attack. (DH28) Percival was convicted and sent to Azkaban, where he would eventually die. To get away from the stigma of the attack, the Dumbledore family moved from Mould-on-the-Wold to Godric’s Hollow.