He was the eldest son of servant and grazier Jeremiah O'Callaghan, publican, and his wife Margaret (née Quinn), he attended Todd's Academy in Sydney and spent much of his childhood in Britain and North America.
Prior to joining the police, he spent some time mining for gold, in what was ultimately a luckless endeavour.
For instance, in 1871, he was demoted for giving alcohol to a prisoner, and in 1882 he was suspended from duty for "disrespectful demeanour towards the Royal Commission on Police".
[2] He was involved in the creation of rules for a board of directors in conjunction with George Turner to streamline the operation of the branches.
Although only newly elected to the Melbourne Branch committee he was appointed by the first annual conference of the ANA as the first chief president of the association.
[1] Having been in poor health for several months, O'Callaghan died on 1 September 1931 at his North Carlton residence, aged 86.
In his novel Power Without Glory, published in 1950, Frank Hardy modelled the "corrupt chief commissioner" Thomas Callinan after O'Callaghan.
To Sub Inspector O’Callaghan
Sir,
The members of the Sandhurst Branch of the Australian Natives’ Association feel that they cannot allow you to sever your connection with them without some expression of the esteem in which you are held by them, and of their good will towards you.
Your association with this Branch has not been an ordinary one. You became a Member at a time of considerable depression in its history and had much to do with infusing the greater vitality and energy that have characterised it for some time past, and the present excellent position of the Branch has been the result.
We feel that you can justly take pride in your share of that result, and that it forms a further illustration of the pre-eminent zeal which from the first you have displayed in
the interests of the Association general.
While recognising the loss our Branch
will sustain by your departure, we heartily
congratulate you on your promotion and wish you every success in the new sphere of action to which your duty calls you.
Signed: Jefferson Connelly, Pres’t.
J.H.Cummin, Sec. J.E.Buchanan, V.P.Chas. Hosking, Magnus Cohn, J.B.Young, W.Beebe Jnr., George Preese, W.May, E.N.Witt, Ass.Sec.
