Biblical Antiquities (Pseudo-Philo) 63
2And at that time came Doech the Syrian, which was over Saul's mules, unto Saul and said unto him: Knowest thou not that Abimelec the priest taketh counsel with David and hath given him a sword and sent him away in peace? And Saul sent and called Abimelec and said unto him: Thou shalt surely die, because thou hast taken counsel with mine enemy. And Saul slew Abimelec and all his father's house, and there was not so much as one of his tribe delivered save only Abiathar his son. The same came to David and told him all that had befallen him.
See also: 1 Samuel 22:18
3And God said: Behold, in the year when Saul began to reign, when Jonathan had sinned and he would have put him to death, this people rose up and suffered him not, and now when the priests were slain, even 385 men, they kept silence and said nothing. Therefore, lo, the days shall come quickly that I will deliver them into the hands of their enemies and they shall fall down wounded, they and their king.
6And after these things Samuel died, and all Israel gathered together and mourned him, and buried him.