I'm not sure that the mayor can legal declare martial law. I think only the governor can. I'm not splitting hairs with you here - I actually believe it is as you say, which is just more sick and wrong.
This is the same mayor that said he couldn't order a mandatory evacuation on Saturday without checking with the legal folks so anything out of him would not surprise me.
I thought it was the Governor as well but in LA all bets are off!