POLICE confirmed they are "not looking for anybody else" in connection with the killing in New Inn on Monday.
A 52-year-old man from Cardiff was arrested by armed police at Newport Railway Station on Monday evening on suspicion of murder, attempted murder and false imprisonment.
He remains in custody and Chief Inspector Huw Nicholas of Gwent Police said.
"The motive of the incident remains unclear," said Chief Inspector Nicholas.
"However, what is clear is that the four victims were restrained and kept in the building for a number of hours before the emergency services were alerted.
"Following the incident a 52-year-old man was arrested at Newport Railway Station. He remains in custody and continues to be questioned in relation to the matter.
"We are not looking for anyone else in connection with this incident.
"Numerous enquiries are being carried out as part of the investigation.
"It is believed that even though no shots were fired, the offender was armed with what appeared to be a handgun and police have today been searching the A4042 where it is believed the suspect discarded the weapon.
"Enquiries have also been conducted at an address in the Rhymney area of Cardiff.’’ He added: "This is a tragic incident and we have specialist staff to support the families of the victims at this difficult time.’’
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