[Autumn]

Hooked Spearhead will proc on abilities that "move" a character attacking someone with the hooked spearhead
for example:

Person A has hooked spearhead
Person B's turn and is using Parting shot

Person B Attacks Person A with handgun and misses them!
Person B takes 30 pierce damage(hooked spearhead proc)

[Neus]

I think it's just Parting Shot. This has been corrected in 1.57b.