20 Now Herod was angry with the people of Tyre and Sidon, and they came to him with one accord, and having persuaded Blastus, the king's chamberlain, they asked for peace, because their country depended on the king's country for food. 21 On an appointed day Herod put on his royal robes, took his seat upon the throne, and delivered an oration to them. 22 And the people were shouting, “The voice of a god, and not of a man!” 23 Immediately an angel of the Lord struck him down, because he did not give God the glory, and he was eaten by worms and breathed his last (Acts 12:20-23).
Unbelievers automatically discount stories about miracles. And they find the account of Agrippa I's demise even more incredible because it dovetails with the trope of villains who get their comeuppance.
Yet Josephus has a parallel account. Moreover, his account reflects a degree of literary license, including legendary embellishment (the omen of the owl), compared to Luke's much more restrained account.
Now when Agrippa had reigned three years over all Judea he came to the city Caesarea, which was formerly called Strato's Tower; and there he exhibited spectacles in honor of Caesar, for whose well-being he'd been informed that a certain festival was being celebrated. At this festival a great number were gathered together of the principal persons of dignity of his province. On the second day of the spectacles he put on a garment made wholly of silver, of a truly wonderful texture, and came into the theater early in the morning. There the silver of his garment, being illuminated by the fresh reflection of the sun's rays, shone out in a wonderful manner, and was so resplendent as to spread awe over those that looked intently upon him. Presently his flatterers cried out, one from one place, and another from another, (though not for his good) that he was a god; and they added, "Be thou merciful to us; for although we have hitherto reverenced thee only as a man, yet shall we henceforth own thee as superior to mortal nature." Upon this the king neither rebuked them nor rejected their impious flattery. But he shortly afterward looked up and saw an owl sitting on a certain rope over his head, and immediately understood that this bird was the messenger of ill tidings, just as it had once been the messenger of good tidings to him; and fell into the deepest sorrow. A severe pain arose in his belly, striking with a most violent intensity. He therefore looked upon his friends, and said, "I, whom you call a god, am commanded presently to depart this life; while Providence thus reproves the lying words you just now said to me; and I, who was by you called immortal, am immediately to be hurried away by death. But I am bound to accept what Providence allots, as it pleases God; for we have by no means lived ill, but in a splendid and happy manner." When he had said this, his pain became violent. Accordingly he was carried into the palace, and the rumor went abroad everywhere that he would certainly die soon. The multitude sat in sackcloth, men, women and children, after the law of their country, and besought God for the king's recovery. All places were also full of mourning and lamentation. Now the king rested in a high chamber, and as he saw them below lying prostrate on the ground he could not keep himself from weeping. And when he had been quite worn out by the pain in his belly for five days, he departed this life, being in the fifty-fourth year of his age and in the seventh year of his reign. He ruled four years under Caius Caesar, three of them were over Philip's tetrarchy only, and on the fourth that of Herod was added to it; and he reigned, besides those, three years under Claudius Caesar, during which time he had Judea added to his lands, as well as Samaria and Cesarea. The revenues that he received out of them were very great, no less than twelve millions of drachmae. But he borrowed great sums from others, for he was so very liberal that his expenses exceeded his incomes, and his generosity was boundless (Antiquities 19.8.2).
So here we have multiple attestation of the same event, from two independent sources.
"Eaten by worms" may well be an idiom or stock phrase rather than a technical diagnosis. Scholars differ on the diagnosis (e.g. peritonitis and/or appendicitis, fecal impaction).