After they die, the two witnesses are caught up to heaven (Revelation 11:12). As James Jordan points out in his lectures on Revelation , this is not the first time someone is caught up to heaven.
Enoch was, so was Elijah. Then Jesus, then the witnesses.
Each is a preacher of righteousness in a world of idolatry and evil. Enoch warns about a coming judgment (Jude 14-15), Elijah preaches against the house of Ahab (1 Kings 17-22), Jesus warns of the destruction of the temple (Matthew 24-25), and the two witnesses breathe out fire in the city (Revelation 11:5).
Jordan points out that there is a progression here: Enoch’s ascension was apparently without witnesses; Elisha alone saw Elijah caught up to heaven; the apostles watched Jesus disappear behind a cloud; but the ascension of the two witnesses is a public event: “their enemies beheld them” (11:12).
Jesus’ vindication is visible only to a few, but the vindication of the church is public. Jesus whispers, but His witnesses shout from housetops.