What? They look like simply people to me. That is a group, not a "gang".
Why the fear? I'm not seeing earmarks of them being threat, just from the photo, though admittedly they could have been 'broadcasting' some form of threat, either expressed or implied when inside the restaurant.
Okay, they look goofy, is that better?
They look like perfectly average if mildly unhappy folks to me, too.