Question: When Henry, Belch, and Victor go down into the sewers in the first part of the movie, I know they separated, but what happens to Victor? All I saw was a bunch of bright light.
Answer: The bright light you saw was IT's dead lights. The appearance of these lights is to signify that Victor is no longer on this earth. Just this happens off-screen. To save money. And to add to the mystery/horror. After all, sometimes it's what you DON'T see that is more scary.
Answer: He was caught and killed by Pennywise, just like Belch is a few minutes later. They just cut away before he dies. But it's easy enough to surmise he's dead given all the context clues the movie gives you.
TedStixon