What is the amount of the blood money (Diyya) in Islamic law for accidental killing, and is it permissible to kill the killer if he does not pay it?

If the killer has no male relatives (عصبة), then the blood money (Diyyah) is taken from the public treasury (Bayt al-Mal). If there is no public treasury, then the Diyyah is taken from the killer's own money, unless the guardian of the victim (Wali al-Dam) pardons him.