I remember thinking at the time that his mom almost seemed like a woman who had been prepared for the tragedy, given her composure and compassion. She alluded to this in the interview, a mother's intuition really is a powerful thing.
We really don't know anything about this Australian guy's character, other than one drunken argument/fight outside a chip shop. We'll also never know for sure whether he actually felt threatened or just wanted to lash out. With this in mind I think it's better for everybody involved that he's just given the benefit of the doubt. I'd like to think that her need for an apology would be recognised and the lad would pick up the phone at some point. He may have felt uneasy about doing so after getting off.
I can't imagine what Gearoid's poor brother must be going through. It's bad enough losing a sibling but to actually witness it happening in those circumstances doesn't bear thinking about. I hope he's as strong as his mother and can find some sort of peace.
RIP