Preflop: Hero is BB with 9 J
CO raises to $0.75, BTN calls $0.75, SB raises to $1.25, Hero calls $1, CO calls $0.50, BTN calls $0.50
Flop: ($5) Q J 9 (4 players)
SB checks, Hero bets $4, CO calls $4, BTN folds, SB raises to $27.32 and is all-in, Hero calls $20.90 and is all-in, CO raises to $42.43 and is all-in
Turn: ($84.54) 6 (3 players, 3 are all-in) River: ($84.54) 4 (3 players, 3 are all-in)
Spoiler:
Results: $84.54 pot ($2 rake)
Final Board: Q J 9 6 4
Hero showed 9 J and lost (-$26.15 net)
CO showed 6 J and lost (-$28.57 net)
BTN mucked and lost (-$1.25 net)
SB showed 9 9 and won $82.54 ($53.97 net)
What do you think the SB was ready to all-in the flop with? Given that he re-raised pre. I put him on premium pairs or AQ+. (except if you have some stats on him 3betting lightly, squeezing lightly etc).
In any case, that shove on the flop doesn't seem to be a bluff. QQ or JJ are very possible in this case. => fold.