죽어버리다 means to die and the grammar point~ㄹ지도 몰라 means could or might

Like Jessica said :) 몰라 by itself does mean "don't know", but in this case 몰라 is part of a bigger picture - the grammar pattern ㄹ지도 몰라. Common struggle with learners is looking at once piece and not realizing it's part of a bigger whole and then as a result not being able to decipher the true meaning.

I'm just learning. I thought 몰라 meant that you didn't know, or don't have knowledge of. I'll be looking out for an actual answer to this too. Thanks, Alina.