I played a [Lightning Bolt](https://gatherer.wizards.com/Pages/Card/Details.aspx?name=Lightning%20Bolt) during my turn (3 damage to target creature or player) to kill a face down creature. Then, my opponent said he was going to morph the creature which was a 0/5 defender with flying ([Monastery Flock](https://gatherer.wizards.com/Pages/Card/Details.aspx?name=Monastery%20Flock)).

Can my opponent morph a dead creature, or does morphing the creature save it because it is a 0/5 and Lightning Bolt only deals 3 damage?