Can a player equip 2 shields?

If yes, can the player STILL attack, using unarmed stats: no power dice, 1 red and 1 green melee attack?

Wanderer999 said:

Yes, as long as he has two hands.

Yes, except you got the dice wrong. An unarmed attack uses no weapon (it does not require empty hands) and uses 1 red dice and no green dice. It does get any melee trait dice (power dice) though as it is still a melee attack.
DJitD pg19
If a hero attacks without a weapon, he attacks with his fists. This is a melee attack that grants one red die and has no special abilities
DJitD pg11
When a hero makes a melee attack , he adds a number of power dice to his roll equal to his melee trait.

Wanderer999 said:

I'm guessing you got these dice from One Fist. One Fist has a special "unarmed" melee attack that gets a green die presumably to represent his hook being better than a bare hand. Everyone else only gets one red die (plus power dice) on an unarmed melee attack.

If One Fist was the hero in question, then it's worth noting that he CANNOT equip two shields because he only has one hand to equip things with. Again, he's different because of his special rules, other heroes have two hands and therefore can equip two shields. If there were a hero released who could use three or four hands worth of gear, they could in theory equip three or four shields if they wanted. It's all about how many hands you have to work with.