Could be an echo. Correct.
Daily Mail has some graphic photos.
Staging area of the victims waiting for transport. Facebook feed:
https://www.facebook.com/permalink.php?story_fbid=1948177205505099&id=100009385140482
Daily Mail (per RSN) reports 1 shooter found on 32nd floor of Mandalay by SWAT. (Unclear if shooter was shot by SWAT or already dead.)