A man in his 50s is in custody in Rome in connection with the brutal murder of three women, who were all stabbed with a stiletto heel, two of whom were killed during sexual intercourse.

Only one of the victims, 65-year-old trans sex worker Martha Castano Torres, has been identified. Police say she was stabbed with the stiletto heel, then shot several times in the chest. She was found in a pool of blood in her bed.

Her sister told police that she told her she was meeting a client shortly before she was murdered. When she didn’t hear from her sister late Thursday, she went to the apartment where Torres allegedly took clients and found blood outside the apartment. She immediately called police who entered the apartment.

The other two women, both believed to be Chinese, have not been identified and did not have documentation on them in the apartment where police say they worked as prostitutes, which is legal in Italy. It is unclear if they are related, but police say all three were killed with the same stiletto used as a murder weapon. Police later found that their “madam” advertised the women as a “pair” to clients on a sex app, but the madam has not been identified.

Police then used surveillance tape footage to identify the potential killer, which led them to the apartment where the other two victims were found, just a block from Rome’s main courthouse in the wealthy residential district of Prati.

A Rome police spokesperson confirmed to The Daily Beast that the man had made an appointment with one of the Chinese women and stabbed her during sex. The other woman in the apartment tried to intervene, but he then stabbed her as well. She tried to escape on the balcony, but he dragged her back inside, where she died. She is thought to have also been raped, post mortem, police say. Both victims were nude when they were stabbed, according to forensic police, who say no bloody clothing was found.

Police used the same chat platform used by the potential killer, who has not been named, to make contact with the victim and identify him as the primary suspect. He was taken into custody Saturday in Rome.

Police were vague about the murder weapon until Saturday, when they said that DNA found on Torres and one of the other victims may match at least two other unsolved murder cases of unidentified sex workers in the Italian capital.