According to Josephus, the Jewish historian in the 1st century CE, Herod Agrippa of Acts 12 “loved to live continually at Jerusalem” and each day offered the prescribed sacrifice of Israel’s king [Josephus: Antiquities 19.7.3]. If this is true, then his leaving for Caesarea should be taken as an indication of his embarrassment over Peter’s escape (cp. Acts 12:19). Certainly, it should be understood that Agrippa would leave Jerusalem from time to time to conduct civil business that needed personal attention that was impossible to accommodate from Jerusalem, but Josephus says his normal abode was in Jerusalem. Yet, Luke claims that Agrippa left Jerusalem and abode in Caesarea (Acts 12:19). Josephus says this occurred when Agrippa was three years into his reign over Jerusalem [Antiquities 19.8.2].
Just before leaving for Caesarea, Josephus records that Agrippa deprived Matthias, the son of Annas, of the high priesthood and gave it to Elioneos, the son of Cantheras. Thus, Agrippa returned the honor to the family of Boethus, the historical favorite of the Herod family, but the rival of the Annas family was the favorite of Rome. It seems that Agrippa was upset with the Annas family, but both Luke and Josephus are silent as to why. It is understandable for Luke to refrain from pointing out a grave error on the part of the Annas family that turned Agrippa against them, since Theophilus is the son of Annas. Moreover, considering the fact that Josephus was Annas’ great grandson through Matthias, the son of Theophilus (son of Annas) who was the last reigning high priest before the Jewish war with Rome broke out in 66 CE, it is also understandable that Josephus wouldn’t want to publicize Agrippa’s anger toward Josephus’ family.
Nevertheless, it seems obvious that Agrippa’s removing Matthias showed he was upset over the advice given him that led to not only killing James but the miraculous escape of Peter, which showed he had acted against God. Agrippa at least went through the motions of worshiping the God of Israel, and wouldn’t overtly offend him. Nevertheless, when he oversaw the summer games held in Caesarea he allowed himself to be caught up in the moment and accepted the worship of the people as they called him a god, because of the beauty of his royal attire. Luke says that an angel immediately struck him and he died (Acts 12:22-23). His death, however, occurred five days later, but he immediately realized his error, according to Josephus:
(345) Soon his flatterers cried out from various places, though not for his good, that he was a god. They added, “Be merciful to us, for though up to now we have reverenced you only as a man, from now on we shall confess that you are above mortal nature.” (346) The king did not rebuke them or reject their flattery as impious. But later he looked up and saw an owl sitting on a rope above his head and immediately understood that this bird was an omen of bad news, as it had once brought him the message of good news, and he felt an ache around his heart. An intense pain arose in his belly that severely affected him from the start. (347) Looking up at his friends he said, “This god, as you call me, is now commanded to depart this life; for that is how Fate punishes the lying words you said to me just now, and I whom you called immortal, am sentenced to death. But I have to accept what God decrees, for we have by no means fared badly, but lived in splendid good fortune.” (348) As he said this, he gasped with pain and he was quickly carried into the palace, and the rumour went round that he was about to die. (349) Straight away the people with their wives and children put on sackcloth, according to their ancestral law and prayed for the king’s recovery and all was full of mourning and lamentation. The king lay in a lofty bedchamber and as he saw them lying prostrate on the ground below, he could not help weeping. (350) After five days tormented the pain in his belly, he departed this life, in the fifty-fourth year of his age and the seventh year of his reign. [Josephus: Antiquities 19.8.2]
Thus, Herod Agrippa perished of the same disease as his grandfather, Herod the Great. I find it interesting that he wasn’t punished for persecuting the Church. He was punished, because, as the king, he took worship that belonged only to God and didn’t rebuke his flatterers. This was very wrong on his part, since he claimed to worship the God of Israel, who knows no gods beside himself. Agrippa was clearly embarrassed over Peter’s escape, and more than likely angered over the poor advice given him by the Annas family concerning the Messianic believers. This is implied in his removing Matthias from the high priesthood and reappointing a member of the Boethus family. The fact Agrippa went no further with the persecution, after executing the soldiers who guarded Peter, implies that he had no personal interest in the deaths of Messianics, beyond pleasing the powerful Annas priestly clan (cp. Acts 12:1-3; note especially “it pleased the Jews” i.e. the Jewish authorities, namely the Annas family of priests). Originally, his vexation of the Church probably included harassment, public ridicule etc., because Messianics served another King, and Agrippa’s prideful heart couldn’t allow that.