Was this a mistake or a bad beat?

[TenFourOff]

1/2 live
Hero on button with A[img]/images/graemlins/diamond.gif[/img]8[img]/images/graemlins/diamond.gif[/img] ~$150 behind
Villian BB with approx $250

PF
three limpers, hero raised to $10, BB called, one other caller, all else fold.

Flop
10[img]/images/graemlins/diamond.gif[/img]A [img]/images/graemlins/club.gif[/img]8 [img]/images/graemlins/club.gif[/img]
BB checked, limper checked, hero bet $25, BB raised to $50, limper folded, hero pushes.