Detectives investigating the murder of gap-year student Marsha McDonnell are linking it with an attack on a teenager on Tuesday morning.
Police sealed off the area
The 18-year-old boy was attacked in Hampton Hill, south-west London at around 0250 GMT, half a mile from where Miss McDonnell, 19, was beaten to death with a blunt instrument.
In another incident, a 17-year-old girl woke up in hospital with head injuries after walking home in nearby Strawberry Hill on 8 January, although she cannot remember being attacked.
Extra police patrols are now in place in the Hampton area.
Detective Superintendent Alistair Jeffrey said: "We are linking these investigations because of the simple facts - they all took place during the hours of darkness, all in the same locality, they were all seemingly motiveless, unprovoked attacks."
"It was probably a lone attacker in each case and in each case it was probably a blunt instrument used as a weapon."
No motive has been found for Marsha's murder
The boy escaped unhurt but shaken after a young man wearing a hooded top ran up behind him and swung at him with a heavy metallic object as he walked into Ormond Drive.
He had got off the N285 bus with two friends in Hampton Hill and was trying to cross the road when he was attacked.
He has not been identified to protect his safety, but will continue to be questioned by detectives on Tuesday evening.
His mother said: "He's very lucky to be alive, we are just relieved he is all right.
"He is still in shock but he is with friends now.
"You worry about them being out at night but you cannot lock them up."
Detectives said the attacker has knowledge of the area which "may indicate he is a local man."
Miss McDonnell was hit three times over the head, yards from her home in Priory Road soon after getting off a 111 bus from Kingston on 4 February.
Superintendent Sue Hill, from Richmond Police, advised residents not to wear headphones when out walking and to be aware.
"Don't think it couldn't happen to you," she said.
"We don't want to raise the fear of crime, however we also don't want another victim."
Hampton residents were extremely concerned to hear about the latest attack.
Max Townsend, 60, said he would be advising his 27-year-old daughter not to go out in the area alone late at night.
He said: "It's very worrying. It just shows that this sort of thing can happen any time any where."