The Haunting in Connecticut

In 1987, Sara Campbell (Virginia Madsen) is driving her son Matthew (Kyle Gallner) home from the hospital where he has been undergoing cancer treatments. Sara and her husband Peter (Martin Donovan), a recovering alcoholic, discuss finding a rental house closer to the hospital. On another hospital visit, Sara finds a man putting up a âFor Rentâ sign in front of a large house. The man is frustrated and offers her the first month free if she will rent it immediately.
The following day, Peter arrives with Matt's brother Billy (Ty Wood) and cousins Wendy (Amanda Crew) and Mary, and they choose rooms. Matt chooses the basement, where there is a mysterious door. After moving in, Matt suffers a series of visions involving an old, bearded man and corpses with symbols carved into their skin. The next day, Peter learns that the house was supposedly a funeral home; the room behind the mysterious door is a mortuary.
Matt tells another patient, Reverend Nicholas Popescu (Elias Koteas), about the visions. Nicholas advises him to find out what the spirit wants. Later, Matt finds a burned figure in his room who begins to move toward him. When the family comes home, they find a shirtless Matt with his fingers blood-covered from scratching at the wall.
The family begins to crack under the stress of Matt's illness and bizarre behavior. The children find a box of photographs, which show Jonah, a young man from Matt's visions, at a sÃ©ance, emitting ectoplasm. Wendy and Matt find out that the funeral home was run by a man named Ramsey Aickman. Aickman also conducted psychic research and would host sÃ©ances with Jonah as the medium. At one sÃ©ance, all those attending, including Aickman, were found dead and Jonah disappeared.
Nicholas theorizes that Aickman was practicing necromancy in an attempt to control the dead and bind them to the house. That night, Nicholas finds human remains in the house and removes them. Matt awakens to find Aickmanâs symbols carved into his flesh. He is taken to the hospital, where he encounters Jonah. Nicholas and Matt begin to have simultaneous visions. Everyone in the sÃ©ance is burnt, after a flash of bright light. The barely alive Aickman told Jonah to get out of the house, concerned that the demonic presence will get him next. Jonah uses a dumbwaiter to escape, calling for help. Entering an unknown chamber, Jonah realizes that he has entered the crematory. The spirit traps Jonah in the crematory, and cremates him alive.
Peter and Sara learn that Matt's cancer treatments have had no effect. They then discover that Matt has escaped the hospital. Back at the house, Nicholas leaves a message telling the family to get out of the house immediately â Jonah's spirit was actually protecting them from the spirits. Matt breaks through the walls in the front room with an axe, revealing the dusty corpses Aickman hid in the walls. He forces Wendy and the children to get out, barricading himself inside and tearing down the other walls, as corpses begin to tumble into the room. The view switches from Matt to Jonah, who seems to be occupying Matt's body. Matt lights the bodies and the room on fire.
As the fire department arrives, Sara and Peter frantically try to get in to save Matt. The spirits, finally freed, disappear. Outside, everyone watches tearfully as the emergency crew attempts to resuscitate a dying Matt. As Matt slips away, he has a vision of himself standing in the graveyard where he sees Jonah, no longer appearing burnt. He seems about to follow Jonah when he hears his motherâs voice.
He returns to his body and Jonah's spirit leaves him. Matt's cancer disappears, and the house was rebuilt and resold with no further reported incidents of haunting.

Question: Who was practicing necromancy?
Answer: Aickman.