if u start worrying abt dreams then u're never gonna b happy.some people do claim that their dreams come true or that their dreams foresee future.but again,we are all different. i was so afraid during my final exams and then i in my dream, i fell from the top of the cliff.guess what happened,i was pessimistic throughout my finals but i made it smoothly to the next level. funny eh? also u see things that u never imazine of doing fo e.g as u said killing someone in dream.man u've just dreamt of killing a bird, i dreamt of killing people.lolz so instead of worrying abt dremas, just try ur best in whatever u're doin.don let something like falling from cliff dishearten u.