Which came after? The only one I’m aware of is the killing of two people with a handgun at Monash University which doesn’t meet the standard definition of a “mass murder”.
A few of the ones off the Wiki page gives:
Monash University (2002)... as you mentioned
Oakhampton Heights Shooting (2005)... mother shoots 3 family members then herself
Hectorville siege (2011)... 3 killed, 3 injured (neighbors/police officers)
Hunt family murders (2014)... Man kills his wife and children
Wedderburn shooting (2014).... man stabs a boy, then shoots parents
Brighton Siege (2017)... labeled by police as 'terrorism', involved the killing of 1 victim and the injuring of 3 more (including police officiers)
Then of course there are a bunch of non-gun related mass killings (by fire/stabbing/etc.)
There may have been a recent murder/suicide, but we have gone from a series of mass murders with high powered rifles in a short time before the ban to none or one in the decades since.
Well, before the Port Arthur Massacre, there was
- The hillcrest murders, where the killer used a winchester rifle (not exactly an "assault" weapon)
- Cangai siege (1993).... I couldn't find a full accounting of the weapons used, but at least one victim was killed with a shotgun, so its possible they didn't have assault style weapons
- Central Coast (1993)... also used a shotgun
- Strathfield (1991) ... used a semi-automatic rifle (again, not an 'assault' weapon)
- Surry Hills (1990)... another use of a shotgun
So that is 6 large-scale shootings in ~half decade prior to the stricter gun laws in Australia. Which is admittedly not good.
But of those,
- Roughly half used 'shotguns'
- 2 others used non-assault weapons. (Yes, they were semi-automatics, but I don't think they would be the type covered by Canada's proposed weapons ban. They were the type that would be used for hunting.)