The two Eoghanist families were represented by Donovan and Molloy.

They were descendants of Oilioll Oluim, from whom Mahoun was also descended, but his family were Dalcassians.

Hitherto the Eoghanists had succeeded in depriving the tribes of Dal-Cais of their fair share of alternate succession to the throne of Munster; they became alarmed at and jealous of the advancement of the younger tribe, and determined to do by treachery what they could not do by force.

With the usual headlong eagerness of traitors, they seem to have forgotten Brian, and quite overlooked the retribution they might expect at his hands for their crime.

There are two different accounts of the murder, which do not coincide in detail.