I spoke with my mate this morning and he said they were notified by Surf WA ( i think he said, the chain of information moves down through three different bodies[}:)]) they were simply told to keep a keen lookout as it was reported 3km out to sea.
He said Ch 7 would have either monitored the Water police radios or possibly been notified by water police.
He actually went on to talk a little more about shark sightings and patrols. He said that the chopper has already been scaled back and he believes that the chopper is one of the better answers to help them notifie people early. He also said though that Surf clubs are having trouble getting people to listen to warnings anyway. They want to police to take more action to have people (especially surfers) charged if they don't get out of the water when warned because its making there job harder to see the shark, often resulting in them then having to get in the water with the shark (all be it in duckies or paddle boards).
I like Shark alarm but find that they get there info a little late as well. They have been chasing for more up to date (time) info from the authorities but i think they are not getting exactly what they are wanting. I wonder if some show of support will help make it a bit more real time and relevant