Registered to post here as the victim was my little brother.
I don't have too much information to add here but I can confirm Neil had an ice-axe and had self-arrest training+practice. From what his climbing buddy said to me, it sounded like Neil started tumbling rather than sliding, which, together with the hardened autumn snow, might have made self-arrest difficult.
Also, I understand they completed the class 4 section but did not summit, because they were just short of the summit at Neil's predetermined turnaround time.
