Not A Conspiracy Theorist, But I Get It

I've never been one of those idiots to go around crying "rigged!", but this hand certainly is one that makes me scratch my head...

Merge Network $200 Freeroll - NL Holdem - No Limit Hold'em Tournament - t75.00/t150.00 Blinds - 9 players
DeucesCracked Poker Videos Hand History Converter

UTG+2: t370.00 2.47 BBs
MP1: t4536.00 30.24 BBs
MP2: t55.00 0.37 BBs
CO: t460.00 3.07 BBs
BTN: t1249.00 8.33 BBs
SB: t2125.00 14.17 BBs
BB: t2145.00 14.30 BBs
Hero (UTG): t3195.00 21.30 BBs
UTG+1: t675.00 4.50 BBs

Pre Flop: (t225) Hero is UTG with K K
Hero raises to t300.00, 5 folds, BTN calls t300, SB raises to t2200 all in, 1 fold, Hero raises to t3195 all in, 1 fold

Flop: (t4850) A 2 5 (2 players - 2 are all in)

Turn: (t4850) 3 (2 players - 2 are all in)

River: (t4850) 8 (2 players - 2 are all in)

Final Pot: t4850
SB shows 3 4 (Five High Straight)
Hero shows K K (Pair of Kings)
SB wins t4850.00

Seriously? Who 3bet shoves 43s? Not to mention that he happens to hit the nuts on the flop? This guy was playing 5/5 over just 39 hands, and that's super nitty. I do find it incredibly suspect.