London’s most notorious serial killer prowled the East End over a century ago, preying on prostitutes and terrorizing the area. He made his mark as Jack the Ripper by killing and mutilating at least five women. Dread grew as the dead bodies began to pile up near each other within a three-month period in 1888. The neighborhood was “horrified to a degree bordering on panic,” when news broke of a second female victim, The Morning Post reported at the time. The local newspaper called the killing “barbarous,” and said the manner of the murder was “too horrible for description.”

Local authorities at first wondered whether the suspect was a butcher or a doctor due to his signature and gory method of murder — and his skill with a knife. The victims of the so-called “Whitechapel Murders” — Mary Ann Nichols, Annie Chapman, Elizabeth Stride, Catherine Eddowes and Mary Jane Kelly — all had their throats slashed, and most of them had their stomachs slit and organs ripped out before being dumped on the streets, according to author Dave Yost, who explores the five deaths in his book Elizabeth Stride and Jack the Ripper.

The FBI, which analyzed the case in 1988 at the behest of a movie production company, said each victim was known to be a heavy drinker and a prostitute. They were all targeted “because they were readily accessible” and were killed swiftly in the early morning hours.

Even with all eyes on the case, police were never able to put a face to the killer. The FBI said local investigations were stymied because forensic technology and other advanced means of thoroughly investigating homicides were “nonexistent” at the time. The National Archives obtained letters exchanged between different law enforcement bosses in 1888 that depict overwhelmed police departments. Charles Warren, who was the chief commissioner of the Metropolitan Police at the time, asked for help from the City of London Police. “We are inundated with suggestions and names of suspects,” Warren wrote.

Countless historians and criminologists — both amateur and professional — have speculated on the killer’s identity, but it appears Jack the Ripper took his secret to the grave.