I don't think the police thinks that the smiley Starbucks guy is the killer, they just want to get their hands on him only to ask some questions about his fashion choices to see if he was involved as a decoy... you know, Thomas Crown Son of Man decoy style..
~Josie~
I also saw that he was not officially a suspect, just wanted for questioning, and the garb he's wearing isn't the same as that the assassin wore.
Edit: or is it she?