This quote obviously refers to the violence by which she dies, which heavily impacts her experience in the afterlife. It also suggests that her injuries, prior to Mr. Harvey killing her with the knife, are serious enough to kill her.

The making of the trap, the luring Susie into it – these are not mere preludes to violence. But links in the chain of violence which culminates in her death.

This act, forbidding Susie to leave, is overtly violent. He is no longer pretending to be nice. His words express the depth of the brutality that will swiftly come.