John the Baptist had come "in the spirit and power of Elias [Elijah]" (Luke 1:17), as the forerunner of Christ at His first coming, and he had been slain. Elijah will actually return as prophesied, as the forerunner of Christ at His second coming, and he also will finally be slain (see note on Revelation 11:3-12). Thus, John was a type of Elijah.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8