Acts 8:1 And Saul approved of their killing him.
A great persecution broke out against the Jerusalem church that day, and all but the apostles were dispersed across Judea and Samaria. The apostles stayed in Jerusalem, however.
But there is another scenario that claims that St. John warned Jerusalem to leave when it was besieged by Roman armies. In Luke 21:20-21, it is mentioned.
20 When you see Jerusalem being surrounded by armies, you will know that its desolation is near. 21 Then let those who are in Judea flee to the mountains, let those in the city get out, and let those in the country not enter the city.
One of the most important facts about St. John is that, in and about Ephesus, he ministered to Christians for three decades, writing the Revelation, the Bible, and three Epistles.
The head of the Asian Church was St. John, and he was targeted for exile to Patmos by the Roman authorities.
Rev 1:9-11
9 I, John, your brother and companion in the suffering and kingdom and patient endurance that are ours in Jesus, was on the island of Patmos because of the word of God and the testimony of Jesus. 10 On the Lord’s Day I was in the Spirit, and I heard behind me a loud voice like a trumpet, 11 which said: “Write on a scroll what you see and send it to the seven churches: to Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia and Laodicea.”