POLICE released four people on bail after a man was found with fatal stab wounds outside a barber's shop in Northolt Village last week.
Adeniyi Lateef Shode, 21, was found bleeding outside the shop, in Ealing Road, just after 9pm on Monday, May 2.
He was found by police and taken to St Mary's Hospital, Paddington, where he was pronounced dead an hour later.
A 19-year-old man was arrested on Monday in connection with the killing. Another man, 20, was arrested with two women, aged 22 and 18, in Berkshire last Friday.
They have all been bailed until June pending further inquiries.
Friends of the victim, known as Enda or Ade, congregated on the green in the village last Tuesday and laid flowers by a tree.
One message read: "I can't believe I'm having to do this for you. You were one of the most amazing people I've ever met, the nicest of them all.
"I'm crying on the outside but smiling on the inside because I never had a bad moment with you, and your smiley face I always looked forward to seeing.
"I just don't understand why anyone would want to do this to you. All my love forever, Alex."
Another message read: "RIP Ade. The good really do die young. You're in a better place now. Lots of love."
Police believe the victim, from Edgware, was stabbed at the junction of Ealing Road, Rowdell Road and Kensington Road, near Belvue Park.
A post-mortem report last Wednesday gave cause of death as stab wounds.
The Homicide and Serious Crime Command is investigating and said it is keeping an open mind regarding any motive.
Detective Chief Inspector Lee Presland, leading the investigation, said: "I would appeal to anyone who may have information regarding this incident to come forward and speak to police."
Anyone with information should call the incident room on 020 8358 0300 or Crimestoppers anonymously on 0800 555 111.