Images of three men who might have information about the murder of a 24-her-old man with the mental age of a nine-year-old have been released by police.
Deam Mayley, from Northolt, was stabbed to death after getting off a bus in Greenford.
He was seen getting off the E9 bus in the Broadway about 50 minutes before he was attacked in Ruislip Road at 5.20pm on Friday, February 7.
Officers and London Ambulance Service attended and Dean was taken to St Mary's Hospital where he died later that evening.
A post-mortem examination took place three days later and found a single stab wound to the chest was the cause of death.
Police are keen to stress that the three men in the images issued are not suspects, but they may hold vital information.
Detectives are urging them to come forward; information that they provide will be treated in the strictest confidence.
The first two images are of two individuals who were present at the KFC in Greenford Broadway prior to the stabbing.
The third image is of a white male who walked pass Dean seconds before the murder.
Dean suffered from microcephaly which led to him having learning difficulties and a mental age of approximately nine years old.
As a result, his family state that he was very vulnerable and easily led.
Detective Chief Inspector Matt Bonner, of the Homicide and Major Crime Command, is leading the investigation.
He said: "I am urging those in the images we have issued to please come forward and help us with our enquiries.
“Likewise there may be people who recognise these three men; don't remain silent please come forward and help us.
"I must stress that we are not treating these men as suspects and strongly believe that any information they hold can assist us with our ongoing enquires into Dean's murder."
Three 17-year-old boys have been accused of the murder and a 19-year-old man was charged with murder.
All appeared in custody at the Old Bailey on May 9. A trial is set to take place on August 4.
Call 020 8358 0200 or 0800 555 111 anonymously.