SafeAtHome, that illustration depicts an event that's supposed to occur after the Millennium where some of Paradise's people turn wicked and threaten those who are faithful.
The idea is based on this scripture from the book of Revelation:
7 When the thousand years are over, Satan will be released from his prison 8 and will go out to deceive the nations in the four corners of the earth—Gog and Magog—and to gather them for battle. In number they are like the sand on the seashore. 9 They marched across the breadth of the earth and surrounded the camp of God’s people, the city he loves. But fire came down from heaven and devoured them. Revelation 20:7-9 New International Version
I remember seeing that illustration in two different places though I can't remember where. I think the image from the book that John Aquila took it from was recycled from some earlier literature. It does look 1960ish in it's artwork.
It's confusing because it mentions Gog and Magog which names are used in a different context in JW teaching.