'Cannibal' killer had attacked previous girlfriend Cerys Marie Yemm, 22, agreed to have a drink in Matthew Williams" room at a homeless hostel after meeting him through friends. Williams, who died after police Tasered him, had promised to order her a taxi after sharing a drink but once inside his room, he killed her. The Welsh Probation Service is understood to have promised a review of its handling of Williams as it emerged he had been released from prison just two weeks ago. He had been halfway through a five-year jail sentence for an assault on a former girlfriend. Williams" family spoke of their "complete shock" at what had happened and said they were "devastated by the death of an innocent young lady." They added: "Words cannot express our grief." Gwent Police said they were treating Ms Yemm's death at the former Sirhowy Arms Hotel, a homeless hostel in Argoed, Blackwood, South Wales, on Thursday, as murder and were not looking for anyone else. They refused to comment publicly on claims of cannibalism on the part of the killer but sources confirmed the victim had suffered substantial facial injuries. A spokesman said: "Our officers who attended the incident yesterday are being fully supported by our force occupational health department." The Independent Police Complaints Commission (IPCC) has launched a separate investigation into Williams" death. The spokesman added: "The murder investigation is continuing today, officers and crime scene investigators remain at the scene. We are co-operating fully with the IPCC, which is independently investigating the death of the man. Chief Inspector Paul Staniforth said: "Speculation about what happened at the scene and the cause of death is unhelpful and very upsetting for the family of the deceased." A post-mortem on Ms Yemm, who worked as a sales assistant for Next, was due to start yesterday but it was unclear when the results would be known. Friends expressed their shock at the death. One, asking not to be named, said: "I feel stunned, shocked and sick to my stomach. It's horrific. She was a lovely person. She didn't deserve to die like that.