Qur'an 2:30 is as follows:
And [mention, O Muhammad], when your Lord said to the angels, "Indeed, I will make upon the earth a successive authority." They said, "Will You place upon it one who causes corruption therein and sheds blood, while we declare Your praise and sanctify You?" Allah said, "Indeed, I know that which you do not know."
As far as I can tell, there is a conversation going on between the God and angels when mankind was not yet created. Basically, God informs His angels that He will create humans and appoint them as a "successive authority" upon the earth. To that angels respond with:
"Will You place upon it one who causes corruption therein and sheds blood, while we declare Your praise and sanctify You?"
My question is how did angels know that ? Do they have the ability to see the future? Or perhaps humans already existed at that time in earth in a "lower status" and were already shedding blood?