BERLIN (AP) — The suspect in a shooting in northern Germany last month that left six people dead was found dead in his prison cell on Tuesday, authorities said.

The shooting in Stade, west of Hamburg, took place on June 29 at a facility that provides temporary accommodation for pregnant women or young mothers with children. The victims were employees of the shelter and of the regional youth welfare office.

Investigators believe the shooting was related to a custody dispute over the 3-month-old daughter of the suspect, a Turkish national born in Germany. He was under investigation on suspicion of murder.

The man, whom authorities have not named, was found dead early Tuesday in his cell at a prison in Bremervörde, near Stade, the regional justice ministry in Lower Saxony said. A doctor determined that he died by strangulation.

The investigation so far indicates that the suspect killed himself, the ministry said. It added that there was no indication of anyone else being involved.