
'Charlie Chop-off' killed and mutilated several young boys in Manhattan, New York.
'Beer Man' stabbed and clubbed to death six people in Mumbai, India.
Jack the Stripper

Although it is not known for certain whether the victims knew each other, it was found that several had ties to the underground pornographic movie scene.
The killings only stopped after the chief investigator into the murders falsely told news reporters that he had narrowed down the pool of suspects to just three people. The names were not announced at the time.
The investigation turned up some interesting clues, such as paint flecks found on several of the bodies, which were traced back to Heron Trading Estate and Scotland Yard's number one suspect, Scottish security guard Mungo Ireland. Ireland took his own life shortly after he was suspected and left a note stating that he could take it no longer and that his wife and the police can find him in the garage. He had died from carbon monoxide poisoning.
Ireland was the number one suspect, clues pointed in his direction and his death and note could be seen as an admission of guilt. However, further investigation showed that Ireland was in Scotland at the time of the final of the six official murders attributed to Jack the Stripper.
There have been other 'prime suspects' over the years with investigators (professional and amateur) and authors coming up with their own. However none have been charged for the murders.
The murders were also known as the Hammersmith Murders and the Hammersmith Nudes Case.
Charlie Chop-Off

On May 15, 1974, a patient of the Manhattan Psychiatric Centre was arrested while attempting to abduct a young boy. This man, Erno Soto, was arrested and added as a suspect of the Charlie Chop-off killings. The only surviving victim of the killer said Soto looked similar to his attacker but would not officially identify him. Soto also confessed to one of the murders.
The problem was that hospital records have Soto in the hospitals custody at the time of at least one of the killings, however, staff also admit he may have temporarily escaped as he had done so several times before. Erno Soto remained in the Manhattan Psychiatric Centre and the killings stopped.
These killings are still officially unsolved.
Beer Man

When it came to give this killer a nickname, the newspapers focused on the most mundane of things found at several of the crime scenes – that two of the bodies had empty beer cans/bottles found next to them, apparently the killers (sometimes/rarely) signature – thus this killer became known as "Beer Man".
A year after the final of these six murders was committed, a man, Ravindra Kantrole, is convicted of a (thought to be) seventh murder. Kantrole is also charged with two of the other Beer Man murders. It was thought a serial killer was now off the streets... however, Kantrole was later cleared of any involvement in the Beer Man killings.
The Beer Man killings are still unsolved.