Very possible that the reference is sunblock, that is a counter-measure to waste the time of anyone trying to track them down and burn them.

Fisher is experienced enough to know any information they leak will be used against them. My guess is that the event is either symbolic or meant build on a persona used to find people like them; post provides a means of contact.

Regardless of their intent, as made clear by my other comment, this was a tragic event, and the police should be held accountable.