How did Daemon receive news of Lucerys death?

There would hardly be witnesses except to see Luke leaving Stormsend and Aemond going right after.
Clearly Aemond looked in shock and if it was an accident, he wouldn't say to anyone rightaway. For Daemon to receive the news could only be through loyal Gold Cloaks or pissed off Mysaria.

I am aware that there are stranger and possibly more crucial holes to be explained but this one rubs me off.