strange set hand

[dark_horse]

this hand was from an online 1/2 NL game from a few nights ago a friend emailed me about. he had no read on villian. was curious what you all thought:

im the button with pocket sixes.

middle raise to 4....2 cold calls behind..i call ..sb folds BB calls...

FLOP 10 6 4 all diamonds...

orig raiser checks.. middle pos bets 7..fold to me..i raise to 14...orig
raiser calls 14 cold..middle pos folds..heads up...

TURN 5cl

check i bet 40...calls...AK? A of Diamonds? or slowplaying a monster? why no
raise??

RIVER 3 BOARD 10 6 4 5 3 no more diamonds..

he bets 70 INTO ME NOW??

what do you do....pots 140 he bets 70...