Here is the situation:
1) Greedo declares an attack against Lando, triggering slow on the draw
2) Lando uses Slow on the draw to perform an attack
3) Lando gets 3 damage through and stun/hide
Greedo is mid-attack (he declared the target but hasn't done anything else) and is now stunned - can he continue with the attack?
If not (we ruled he could not), does he still get that action back or is it lost? (we ruled he lost it).