I created a rule for myself a long time ago in online poker. The rule is, where there is one pp there is another. It has worked and has held true to me to this day. So if you get dealt a pp its more then safe to assume there is another pp in someones hole cards at your table. With 77 after your raise he reraises like that I would bet he has 1010 or above or a10 or above giving him 2 overs at least. Of course this is just based off the information you gave. I am not there seeing how he is playing. If he is playing every hand and extremely loose like that ect ect lots of variables can change how you decide to play the hand. But basic 101 poker here says fold all over it.