No one knows but here are the five primary suspects.
1) H.H. Holmes (pictured below) was an American serial killer
and physician who had the medical know-how to dissect bodies as the Ripper did.
He was in London at some point and later confessed to a number of murders in
the US where he was later executed.
2) Aaron Kosminski was a Polish Barber who lived in Whitechapel
at the time of the Ripper murders. He had homicidal tendencies he was sent to a
mental institution in 1891 as a suspect in the murders.
3) Prince Albert Edward Victor was Queen Victoria's grandson. A
major suspect in some quarters but Royal record show wasn't even in London at
the time of the murders.