TWO teenagers have been arrested on suspicion of murdering a vulnerable man, who was killed in a street stabbing.
Dean Mayley, 24, who had the mental age of a nine-year-old, was going to visit his uncle in Greenford when he was attacked.
Dean, from Northolt, was taken to hospital where he died later that evening.
Two 17-year-old boys were arrested and are being held in custody on suspicion of murder.
Dean suffered from a disorder which led to him having moderate learning difficulties. It meant he rarely left home alone, except to visit relatives.
A post-mortem gave the cause of death as a single stab wound to the chest.
Detectives have released CCTV footage showing some of Dean's last movements.
He is seen getting off an E9 bus in Ruislip Road East, Greenford, at around 4.25pm on Friday, February 7 and walking away in the direction of The Broadway.
Around 50 minutes later, he was attacked by a group of three or four young men - described as black and wearing dark, hooded tops - and stabbed to the chest with such ferocity that his heart was pierced.
Det Chief Insp Matt Bonner, said: "I hope this footage might help people to recall the events that led to Dean's tragic death.
"This was a vulnerable man who would have shown an unusual degree of trust in those he came across and it is utterly sickening he should have been set upon in this way."
The incident room can be contacted on 0208 358 0200 or you can call Crimestoppers anonymously on 0800 555 111.
This picture of Dean has been issued. It shows him hugging his seven-year-old nephew, Callum, and Dean's family have described the pair as 'inseparable'.