March 11 (UPI) -- Angus Robertson Sinclair, one of Scotland's most notorious killers, died in prison Monday at age 73, authorities said.
Sinclair was serving a life sentence for a number of killings and sexual attacks when he died. He spent a total of 40 years behind bars for various crimes, including one of the longest sentences ever handed down by any court.
A cause of death was not immediately announced and officials said they are investigating.
Among Sinclair's victims were two 17-year-old girls who were strangled in what became known as the World's End murders. Sinclair killed Christine Eadie and Helen Scott after a night at Edinburgh's World's End pub in 1977. It took decades to link Sinclair to their deaths but police investigators finally did after years of investigating.
Sinclair has been blamed for a number of other unsolved rapes and killings and served more than 30 years in prison before the life sentence was handed down.
At age 16, Sinclair strangled a 7-year-old girl to death in Glasgow, for which he pleaded guilty to manslaughter and served only six years in prison. Police used DNA to link Sinclair to the death of Mary Gallacher, who was raped and stabbed near a Scotland rail line.