Doeg the Edomite, he killed eighty-five men who wore the linen ephod

1 Samuel 22:1-23
David left Gath and escaped to the cave of Adullam. When his brothers and his father’s household heard about it, they went down to him there. All those who were in distress or in debt or discontented gathered around him, and he became their commander. About four hundred men were with him.
But the prophet Gad said to David, “Do not stay in the stronghold. Go into the land of Judah.” So David left and went to the forest of Hereth.
Saul Kills the Priests of Nob
But the king’s officials were unwilling to raise a hand to strike the priests of the Lord. The king then ordered Doeg, “You turn and strike down the priests.”So Doeg the Edomite turned and struck them down. That day he killed eighty-five men who wore the linen ephod. He also put to the sword Nob, the town of the priests, with its men and women, its children and infants, and its cattle, donkeys and sheep.
But one son of Ahimelek son of Ahitub, named Abiathar, escaped and fled to join David. 
David and his whole family are outlawed or in exile. But still, Saul is not satisfied. There seems to be more than a touch of paranoia in his outburst. Ignoring the voice of truth and reason he orders first the slaughter of God's priests and then the death of all the inhabitants of Nob. When David hears the news, it is with an awful sense of responsibility.
Why?
Saul angry to everyone helped David. So he killed the family of Nob and his whole Priest family. It was against the Lord and did not fear the Lord.
David became a leader of 400 men who are distress, in debt or discontented. But with these, they could do something.
How?
Actually, Nob did not wrong but lose his life with his whole family, This is a disaster but God has his way to revenge.