Claire's not killing anyone. She's trying to warn them. You see, sometimes spirits, they don't want vengeance, they want justice. Which is why she led us here in the first place. She wants us to know who her killer is... Detective, how much do you know about your partner?
A death omen is an apparition of a deceased person or object. Usually, a death omen is an indicator that the person who is visited by it is going to die. The apparition can manifest in several places at once (bilocation), and to different people. Sometimes a death omen will try to communicate with the person they are appearing to, in order to warn them against impending danger.BoM
The ghost of Claire Becker is a death omen who was killed by a crooked detective, Pete Sheridan. She appears to people he is about to murder. She tries to communicate and generates the letters "DANASHULPS" through printers, and computers. This is an anagram of Ashland Sup(plies), where she was killed.
When Diana Ballard kills Sheridan, Claire is put to rest.
The ghost ship Espírito Santo appears to people who have murdered a member of their family, before they are killed by the vengeful spirit of the Captain's brother. The ship also appears to Bela, who does not elaborate on the reason.
After the brothers summon the spirit of the Captain and the two spirits merge. The ship is not seen again.
In the present day, angry that other, often fake, psychics are successful while he isn't, Jimmy Tomorrow binds the ghost of Margaret Fox to kill them. Her sister Kate tries to warn the victims of their impending death.