A serial killer, or quite possibly a group of serial killers, are terrorising the Konibodom area in northern Tajikistan, with at least 13 people murdered in their homes since late March, according to local reports.

Locals speak of men clad in black who break into homes and kill the occupants.

There is no precedent for these serial murders, not only in Konibodom, but across Central Asia, according to a June 19 report from The Times of Central Asia.

People are locking themselves in their homes when darkness falls, while some are arming themselves and some have fled the locality, situated in the western Fergana Valley on the border with Kyrgyzstan, it said.

Local police appear to have no idea as to the identities of the killer or killers, nor has a credible theory been advanced by investigators as to why the murders are happening.

The trail of horror began with the killing of five members of the Sharipov family. At first, investigators believed the 65-year-old head of the household killed his wife, daughter-in-law and two grandchildren, then hung himself—but they later concluded that a killer broke into the home, and hung the man to make it look like a domestic dispute with a subsequent suicide.

Among other victims are a husband and wife that police said suffered a violent death, and a mother and her two children, as well as the deputy director of a local school, her brother and the brother’s wife. Local law enforcement reportedly stated that preliminary evidence showed all of the latter six people were strangled.