No reads, just sat down. What is villain raising with and is shoving correct or do I just flat?

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

Stacks:
UTG ($25.00)
UTG+1 ($13.55)
CO ($40.70)
BTN ($35.75)
SB ($37.85)
Hero ($25.60)

Pre-flop: ($0.35, 6 players) Hero is BB [6h]
2 folds, CO raises to $0.85, BTN calls $0.85, SB calls $0.75, Hero calls $0.6

Flop: [4h][8h] ($3.4, 4 players)
SB checks, Hero checks, CO checks, BTN checks

Turn: ($3.4, 4 players)
SB checks, Hero checks, CO checks, BTN checks

River: ($3.4, 4 players)
SB bets $1.25, Hero raises to $4.75, 1 fold, BTN calls $4.75, SB raises to $18, Hero ???

I have no idea how to post a hand output but I just ran our hand against:

Any Ax suited, any hand containing a 4 (both suited ad unsuited) as well as 44 and 88.

Against that range our equity is 99.231 vs. his 0.769

So there's only 2 hands that beat us than make up about less than 1% of his range. So in all honestly I really don't care what he's raising with...... Mallin if he has 44 or 88 so be it but there's no way I'm folding a boat here.

Yeah this is a no-brainer shove, he can't fold

this is a straight, flush, lone 4, 84 alot

I guess he had 88/44 but don't fool yourself that anyone can fold this.