Villain is 21/21/3 over 19 hands and is playing 8-tables. I sort of put out a block bet on the river but when he shoves this is a fold, right?

$0.1/$0.25 No Limit Holdem
6 players
Converted at

Stacks:
UTG ($33.20)
UTG+1 ($23.15)
CO ($5.15)
BTN ($24.65)
Hero ($30.65)
BB ($37.00)

Pre-flop: ($0.35, 6 players) Hero is SB [Ks]
3 folds, BTN raises to $0.85, Hero raises to $2.8, 1 fold, BTN calls $1.95

Flop: [7h][6d] ($5.85, 2 players)
Hero checks, BTN checks

Turn: ($5.85, 2 players)
Hero bets $4, BTN calls $4

River: ($13.85, 2 players)
Hero bets $6.5, BTN goes all-in $17.85, Hero ???