He was killed by a hollowgast before the beginning of the series. His body was kept in a locked room upstairs in Miss Peregrine's Home For Peculiar Children, near Emma Bloom's room, before the children bury him after the loop's collapse.
Victor and his younger sister Bronwyn used to live in Swansea, Wales, with an abusive and toxic stepfather. At age 10, Bronwyn snapped the stepfather's neck.
At some point, the siblings began living in Miss Peregrine's Home. During Victor's stay, he apparently once sank the Cairnholm ferry with all the peculiars aboard, which severely angered Miss Peregrine.
Victor wasn't too fond of life in the loop, which eventually prompted him to leave one day.
Victor Bruntley was killed by a hollowgast after leaving Miss Peregrine's loop when he "couldn't stand it any longer", as Emma explains to Jake. In an earlier chapter, it is revealed by Enoch that Victor's death is the reason that Miss Peregrine wears black, and is very strict on the matter. It is unsure how the peculiars retrieved his body. It can only be assumed Miss Peregrine had retrieved it.
Victor, like his sister, Bronwyn Bruntley, has the peculiarity of super strength. One feat of his peculiarity included lifting a boulder with a single hand. Both are said to be as strong as ten men.
Jacob meets Victor when Victor is dead. At first, Jacob thought he was sleeping, but then discovers that he is no longer alive.
In the film, Enoch uses one of his hearts to briefly bring Victor back to life. He does this to scare Jacob. We can only infer that, before Victor's death, Enoch and Victor were great friends because when they were burying him, Enoch gave Victor one of his favorite homunculi.
Victor's younger sister, Bronwyn, is very sensitive over the topic of her older brother and is brought to tears by the sight of his body.
On the subject of Victor, Miss Peregrine is said to be very stern and would punish the children if she had known they entered the room where he lay. She always wears black because of his death.
In Chapter 9 of Miss Peregrine's Home for Peculiar Children, Emma tells Jacob about what caused Victor's death and why it happened. She also expresses sympathetic feelings toward Victor over the matter.