Shgagah with the killing of the son of the Amalekite ger?
In Shmuel 1:31:4 it says that Shaul committed suicide rather than be captured alive by the Plishtim.
Later, in Shmuel 2:1:2-15 it says that the son of an Amalekite ger who was in the ranks of Shaul's army came to David and claimed that he had killed Shaul as an act of mercy. It's clear he wished to find favor in the eyes of David, but this backfired and David commanded one of his men to kill him because he killed "Mashiach Hashem", Shaul.
Considering that we know from the Tanach that the man was lying, hypothetically, if David had learned the truth - would he have been guilty of murder b'shgagah (with all the dinim that come with that status)?