I thought he had top pair and i could push him off of it with that scary turn card. With a closer look though, it completes straight and flush draws which are certainly in his range so I think that this was a bad turn card to double barrel.

What types of cards are we looking for when we double barrel?

PokerStars No-Limit Hold'em, $0.10 BB (9 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

saw flop

BB ($12.40)
UTG ($10.75)
UTG+1 ($2.10)
MP1 ($2.95)
Hero (MP2) ($10.85)
MP3 ($12.85)
CO ($4.05)
Button ($1.85)
SB ($5.90)

Preflop: Hero is MP2 with 4, 4
3 folds, Hero raises to $0.40, 3 folds, SB calls $0.35, 1 fold

Flop: ($0.90) 10, 5, 6 (2 players)
SB checks, Hero bets $0.60, SB calls $0.60

Turn: ($2.10) 9 (2 players)
SB checks, Hero bets $1.20, SB raises to $4.20, Hero folds

Total pot: $4.50 | Rake: $0.20