Below is a list of the casualties from the 2 Event Horizon operations conducted
Crew of the Event Horizon - All crew members (18 people) were killed using self-mutilation and murder as they went into "hell". At least one man was eaten alive by fellow crew members and one woman was raped while being stabbed. John Kilpack the Captain of the Event Horizon, had his eyes forcibly gouged out and was found with deep lacerations across his face, presumably causing his death by blood loss.
Peters - Fell to her death after following a hallucination of her son. She fell at least 2 stories, hitting the sides of a shaft on the way down, and hit a metal ramp connected to the gravity drive and turning the water surrounding the drive red with her blood. She takes a few breathes and looks up at the manifestation of her son smiling before dying. Its likely a broken neck or shock killed her
Smith - Is killed when a bomb Weir plants on the Lewis and Clark explodes. After he sees Weir leaving suspiciously from the Lewis and Clark and after being informed that Weir planted a bomb on the ship, he begins searching for it as he had already worked 17 hours fixing the ship and couldn't stand all of his work being wasted. When he finally found the bomb, he discovered it only had a few seconds till it blew up. He hung his head and the bomb exploded in his face, destroying the Lewis and Clark and killing Smith, launching cooper.
D.J - Is violently vivisected by Weir. After being blind-sided and knocked out by the now insane and eyeless Weir, he is laid on an operating table and has an autopsy performed on him while still alive by Weir. His body is then hung up on wires and held open by Weir, exposing the inside of his body. Based on the information from the film, it can be concluded that DJ was dead when Miller reached the Medical. However, according to the original script, DJ was alive when Miller came and begged him to put him out of his misery.
Weir and Miller? - It is implied that Weir and Miller will be killed as they get teleported to the Chaos universe and as shown in the video taken of the original crew, they will be victims of mutilation and eventual death. Its also possible that Miller died in the Explosion and that weir actually died in the vacuum of space.