he has now put in 30% of his effective stack so probably isn"t folding. You have the option to fold or shove as calling cant really be an option now. How you procede from here is very read dependent and it is a tough spot. i see this move quite a bit in low stakes STTs. It can be big pair (QQ+) but I have seen weak players (trying to represent a monster) do this with very marginal holdings. (Ax, TJ, TQ, TK, JQ and maybe JK) Other holding such as pairs 22-JJ and AK, AQ, AJ, KQ would surely come in for a raise preflop.
Most of the time, online, I would shove over the min reraise, get called and am ahead most of the time. But that is with a bigger blinds to stack size.
In a live situation, my inexperience would probably get the better of me and I"d take the weak option of calling because I wouldn"t have the bottle to shove them in, unless i had a "Janet and John" read that he was weak and couldn"t bear to fold AJs in a HU situation. I"d then leave myself in a whole lot of bother going to the flop.
You also have to consider your mental state at this point. You have come back from the dead and are looking good now. Do you want to blow it all in a HU battle of egos? Or is this a great spot to challenge for the chip lead? I think letting it go is good. You are still pretty healthy. I"d also try and get the guy to show his hand as well.