Bought in 1k at a 2-5 Aria game. (8 handed)

The first hand I sit down I get 8d8s UTG+1 on a UTG straddle.

Hero: Raises 35.
LJ (Effective stack 800): Flats.
SB: (Effective stack 1500): Raises 95. (First impression seems fishy by his bet sizing and gut feeling looks like the type that could be aggro.)
Hero flats
LJ flats

Flop: 245ddd
Checks around.

Turn 2c.
Sb leads 95.
I flat.
LJ folds.

River is Js.
Sb bets 700.

I folded.

Was wondering if it was a good fold and what could he possibly have and any other suggestions playing the hand?

(Later was told by a player that he check raised him on an aa3 board with K9 thus my assessment of him being bluff capable was right).