The Illustrated London News in February, 1871, caught my eye because of its reference to "the shot this time knocking off the hat of the servant". This event occurred on either January 22nd or 23rd, 1871. I did a little digging and it seems that Mr. Blagriff's residence is nowadays the Glasson Golf Hotel, although I haven't been able to confirm that. I found another report of the incident, printed in New Zealand's Daily Southern Cross, of March 28th, 1871. The final couple of lines are golden.
Bureau Of Military History 1913-1921 witness statements. This, from Henry O'Brien, of Athlone:
I've no evidence that these people were related although how close they lived to each other suggests strongly to me that the man executed was a grandson or maybe grandnephew of the man shot at in 1871. If anyone has any more information on either men I'd love to hear it so please comment.