John Dunn was born at Murrumburrah, (NSW) on 14th December, 1846, one of nine children born to Michael Dunn and Margaret nee Kelly. Like the majority of the young lads reared in the bush, he was an excellent rider, who at seventeen years of age had won the main prize at the Yass races in.

Shortly afterwards he joined up with the Hall - Gilbert gang, and straight away he proved his "efficiency" as a bushranger-to-be by stealing several good race horses. In November 1864, he accompanied Hall and Gilbert for two weeks, robbing the mails to and from Gundagai. The police were expecting that the hold-ups would continue, therefore on the next day two of them travelled in the coach as passengers in private clothes, and another two rode beside the coach. The bushrangers indeed turned up at Black Springs and a terrible fight took place, in which Gilbert shot dead Sergeant Edmund Parry. When the police were overpowered, the robbers collected everything, and shouted: "We'll rob the mail tomorrow if all the bloody traps in the colony are here!", before they disappeared into the bush. Still, many more armed hold-ups and shoot outs were to follow.

In January 1865, the gang bailed up Kimberley's Inn at Collector, took people prisoners and ransacked the place. Constable Samuel Nelson, the sole policeman in the township and father of eight children, went to investigate, flanked by his son. Suddenly, Dunn, who was hiding behind a fence post armed with a gun, called on Nelson to "stand". The constable was still advancing as Dunn shot him in the chest, and finished him yet with another shot from his revolver. Then he fired at his unarmed son, who luckily ran away. Gilbert, on hearing the shots, came out of the Inn to investigate and robbed the dead Constable of his belt and carbine. More horrible atrocities continued until on the 6th May 1865, when the leader of the gang, Ben Hall, was shot dead, and on the 10th, John Dunn and Johnny Gilbert were outlawed. They sought refuge at a farmhouse of Dunn's grandfather Kelly, but the police caught up with them. Gilbert was shot by the police on the 13th May, and by the death of this notorious scoundrel, the gang broke up. Dunn escaped and went into hiding. For eight months he was not heard of, then he emerged at his old haunts in the Lachlan district. He was finally captured by the police on Boxing Day, 1865, after a shoot-out, in which Dunn and an arresting Constable were wounded. Dunn was taken to Sydney, where on the 19th of January he was tried, found guilty, and sentenced to death. When he was hanged on the 19th March, 1866, he was not yet twenty years of age. He was buried in the old Devonshire Street cemetery. A headstone was erected by Mrs Pickard, Dunn's Godmother, which read: "Memory of John Dunn, who died March 19th, 1866. Aged 19 years. May he rest in peace. Amen. He has gone to his grave but we must not deplore him though sorrow and darkness encompass his tomb - the Saviour has passed through its portals before him and the light of his love was the lamp through his doom".