Not much data on this guy except that he sat down at the table and played about 18 of his first 20 hands, raising about 1/2 of them.

Did I handle him correctly or was the turn bet too risky?

Party Poker No-Limit Hold'em, $50 (4 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

Hero ($49)
BB ($76.90)
UTG ($43.67)
Button ($82.99)

Preflop: Hero is SB with K, A. Hero posts a blind of $0.25.
1 fold, Button raises to $1, Hero (poster) raises to $2.25, 1 fold, Button calls $1.50.

Flop: ($5.50) 8, 9, 6 (2 players)
Hero bets $3.5, Button calls $3.50.

Turn: ($12.50) 3 (2 players)
Hero bets $8, Button folds.

Final Pot: $20.50