Good player: What is he doing?

[DeuceKicker]

Party .5/1

I didn't play this hand, but I was watching and I'm still baffled by it.

EP2 is a little loose-passive, MP2 is loose-aggressive, and MP3 is a player who I've played hundreds of hands with and know him to be a very solid, tight-aggressive player.

EP2/LP has J[img]/images/graemlins/club.gif[/img] J[img]/images/graemlins/diamond.gif[/img]
MP2/LA has A[img]/images/graemlins/club.gif[/img] T[img]/images/graemlins/club.gif[/img]
MP3/TA has Q[img]/images/graemlins/diamond.gif[/img] Q[img]/images/graemlins/spade.gif[/img]

EP2/LP raises, MP1 calls, MP2/LA calls, MP3/TA 3-bets, Button folds, SB folds, BB folds, EP2/LP calls, MP1 calls, MP2/LA calls

Flop(14 SB): A[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/diamond.gif[/img]

EP2/LP checks
MP1 checks
MP2/LA bets
MP3/TA raises (raise with an A on the board?)
EP2 calls, MP2 calls

Turn(16 BB): J[img]/images/graemlins/heart.gif[/img]

EP2/LP bets (liked J. Pre-flop raise probably means set)
MP2/LA calls (GOT to have an Ace, right?)
MP3/TA raises (again?)
EP2 calls, MP2 calls

River(22 BB): Q[img]/images/graemlins/club.gif[/img]

EP2 checks, MP2 bets, MP3 calls, EP2 calls

So he riverd his set, but I still don't get it. I haven't seen this guy make a maniac play like this in hundreds of hands. I don't think he was advertising a maniac move, because I think he knows few at this limit would notice.

Can anybody offer any insight? I'd be surprised if he wasn't a reader/contributor here, so if he remembers this hand maybe he'll tell me his reasoning so I can sleep tonight.