According to Roman Catholicism, how many times is Elijah going to come back?

This question (and its answers) indicate that, according to Roman Catholicism, the two witnesses prophesied to come in Revelation 11:3 will almost certainly be Enoch and Elijah (Elias). > And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth. Part of the reasoning leading to this notion is that neither of these man died physically but both were taken up into heaven alive and, since it is appointed for man once to die and then the judgement (Hebrews 9:27 ), it is within the integrity of Scripture for them to return where they will eventually be killed by the beast from the bottomless pit. > And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them. And their dead bodies shall lie in the street of the great city, which spiritually is called Sodom and Egypt, where also our Lord was crucified. And they of the people and kindreds and tongues and nations shall see their dead bodies three days and an half, and shall not suffer their dead bodies to be put in graves. And they that dwell upon the earth shall rejoice over them, and make merry, and shall send gifts one to another; because these two prophets tormented them that dwelt on the earth. - Revelation 11:7-10 This is coupled with the prophet Malachi (4:5) declaring: > Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the LORD: With the conclusion being that, even though they are not named in the Apocalypse, Elijah will almost certainly be one of the two end times witnesses because he has yet to die in fulfillment of Scripture and he is prophesied in Scripture to come again. Jesus, however, in Matthew 11:10-15 , clearly said that John the Baptist was the prophesied appearance of Elijah and directly quoted Malachi. We also know from Matthew 14 that John the Baptist was put to death by beheading. Additionally, at the transfiguration event recorded in Matthew 17 wherein Moses and Elijah appeared with Jesus to three of the disciples, the disciples asked specifically why the scribes say that Elijah must come first and, once again, Jesus declared that John the Baptist **was** that coming of Elijah: > And his disciples asked him, saying, Why then say the scribes that Elias must first come? And Jesus answered and said unto them, Elias truly shall first come, and restore all things. But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them. Then the disciples understood that he spake unto them of John the Baptist. - Matthew 17:10-13 My question is: According to Roman Catholicism, since Elijah has already come back and died (fulfilling Malachi, Hebrews 9, and the RC argument literally), how many more times is Elijah coming back to earth to be killed and why?