"While they were killing and I was left alone, I fell facedown, crying out, 'Alas, Sovereign Lord! Are you going to destroy the entire remnant of Israel in this outpouring of your wrath on Jerusalem?' He answered me, 'The sin of the people of Israel and Judah is exceedingly great; the land is full of bloodshed and the city is full of injustice. They say, "The Lord has forsaken the land; the Lord does not see." So I will not look on them with pity or spare them, but I will bring down on their heads what they have done.'" NIV translation
A true prophet has a broken heart when he sees people being judged and Ezekiel fell down and cried out to God for the people. Their sin is described as "exceedingly great" and this is talking about the fact that, once they turned their backs on God, there was no alternative to punishing them. The people had rejected God and so they were going to be covered in their own blood.