I can't compleite this mission

[♡♥♡Wei♡♥♡]

In the mission "Under Servalance" I killed the guys in the van and the guys on the fountain, but I can't kill the last guy on the skyscraper, he like dissapears or hides or something and if he is hiding, he's not coming out I took a screenshot http://steamcommunity.com/sharedfiles/filedetails/?id=374685676 what do I do?

[masterchef]

You need stay on top the casino -> look this: https://www.youtube.com/watch?v=0WWzi5wLsIE