set facing 3 bet on flop

[jlmcrna]

Beaurivage this past weekend (WPT Gulf Coast Championship).
2/5 NLHE

10 handed

Im in BB(575) pf with 77. utg(t400) calls, utg1(300) calls, mp2(500) and mp3(600) call, button(300) calls, sb(900) calls, i check.

Flp comes KhTh7c
I lead out for 35, utg calls, utg1 folds, mp2 raises to 100,mp3 reraises to 300, button and sb fold to me.

What is this guy likely holding and what is the best line?