And he killed - He caused to be put to death with a sword, either by beheading, or piercing him through. The Roman procurators were entrusted with authority over life, though in the time of Pilate the Jews had not this authority.
James, the brother of John - This was the son of Zebedee, Matthew 4:21. He is commonly called James the Greater, in contradistinction from James, the son of Alpheus, who is called James the Less, Matthew 10:3. In this manner were the predictions of our Saviour respecting him fulfilled, Matthew 20:23, "Ye shall indeed drink of my cup, and be baptized with the baptism that I am baptized with."

He killed James the brother of John with the sword - This was James the greater, son of Zebedee, and must be distinguished from James the less, son of Alpheus. This latter was put to death by Ananias the high priest, during the reign of Nero. This James with his brother John were those who requested to sit on the right and left hand of our Lord, see Matthew 20:23; and our Lord's prediction was now fulfilled in one of them, who by his martyrdom drank of our Lord's cup, and was baptized with his baptism. By the death of James, the number of the apostles was reduced to eleven; and we do not find that ever it was filled up. The apostles never had any successors: God has continued their doctrine, but not their order.
By killing with the sword we are to understand beheading. Among the Jews there were four kinds of deaths:
1. Stoning;
2. burning;
3. killing with the sword, or beheading; and,
4. strangling.
The third was a Roman as well as a Jewish mode of punishment. Killing with the sword was the punishment which, according to the Talmud, was inflicted on those who drew away the people to any strange worship, Sanhedr. fol. iii. James was probably accused of this, and hence the punishment mentioned in the text.

And he (b) killed James the brother of John with the sword.
(b) Violently, his cause not being heard at all.

And he killed James the brother of John with the sword. This was James, the son of Zebedee, whom our Lord told, that he should be baptized with the baptism he was baptized with, Matthew 20:22 meaning the baptism of martyrdom; and he was the first martyr among the apostles: the death he was put to was one of the four capital punishments among the Jews, and was reckoned by them the most disgraceful of them all, and was inflicted upon deceivers of the people; and such an one James was thought to be (e).
(e) Misn. Sanhedrin, c. 7. sect. 1, 3. & 11. 4.

killed James . . . with the sword--beheaded him; a most ignominious mode of punishment, according to the Jews. Blessed martyr! Thou hast indeed "drunk of thy Lord's cup, and hast been baptized with his baptism." (See on Mark 10:38-40.) A grievous loss this would be to the Church; for though nothing is known of him beyond what we read in the Gospels, the place which he had as one of the three whom the Lord admitted to His closest intimacy would lead the Church to look up to him with a reverence and affection which even their enemies would come to hear of. They could spring only upon one more prized victim; and flushed with their first success, they prevail upon Herod to seize him also.

He killed James the brother of John. One of the three apostles most intimate with the Savior. The first apostle to suffer martyrdom. He is the only apostle whose death is recorded in the New Testament, save Judas the betrayer.
With the sword. He beheaded James. This James, the apostle, is to be distinguished from James, the brother of the Lord (Galatians 1:19), whose name appears after this in Acts, and who wrote the Epistle of James.

James the brother of John - So one of the brothers went to God the first, the other the last of the apostles.