Im quite surprised by many of the comments on this, yes it was someone who obviously didn't understand the local fishing rules and regs. However if it had been a rod and reel angler catching any of the gropers I so often see and hand feed while on scuba or spearfishing it would be considered quite ok for them to catch and kill it. For years I dived with both scuba and free dive a location which had a fair sized groper of just under 15kg which I would never consider targeting with rod and line. It was a rod and line angler who killed it for a inter club competition where he was congratulated by just about every person from all clubs on his catch. It was also the species he targets more than any other species of fish. Personally even though I have my favourite species to interact with under water, I see no difference in catching and keeping a kingfish, tuna, marlin etc over a groper. Those who get under the surface will also know that kingfish can be just as curious and interact with you much like groper. Wrasse are even more interactive than groper, yet people will often discard them as a rubbish catch for the cat. Unfortunately for some fish if they don't look the part they aren't treated with the same respect all fish should have.
Over this Xmas holiday fisheries have been catching many anglers in my area for having undersized kingfish. There have been a fair amount of undersized flathead and snapper also among local catches. There have been numerous boats in the various sanctuaries here also fishing, to the point I can guarantee seeing boats in these areas on every trip. Yes fisheries hand out warnings to people from outside the area but then come down harder on second offences. What Im saying here is this is a daily thing happening here not a mistake someone has made for the first time on a 40yr old fish, if they had it wouldn't of been 40 years old.
I would be extremely surprised if this person was aware he had done wrong until he got mobbed on the rocks as many other states allow for them to be speared. Yes someone made a mistake and he now needs executing by the angry mob with any other fishing person who may of ever drifted into a marine sanctuary, exceeded a no wash speed limit or forgotten to check the dates of their life jackets.
https://www.theinertia.com/environment/why-spearfishing-isnt-all-just-blood-and-guts/