A close friend who released the image told how he narrowly escaped death himself after leaving 27-year-old Oliver to get some food just moments before the attack.
His pal returned to find him dying from what he says was up to six bullet wounds, including one that he thinks penetrated his heart.
The friend said: “I found Oliver lying flat out and I thought somebody had punched him. I tried to wake him up and felt for his pulse and then started giving him mouth-to-mouth and pumping his chest.
“The police arrived and cut off his clothes and that’s when I saw about five holes in his chest including one in his heart.
"He had another bullet in his thigh. He looked really peaceful. I was just calling his name.”
The suspect got out of a dark hatchback and shot Oliver at close range before returning to the car and speeding away.
Two men have recently been arrested and bailed in connection with the murder .
'He was staying with me because he had nowhere else to go'
Oliver had been due to appear in court the next day accused of assault, criminal damage and being drunk and disorderly.
The troubled young man is said to have been homeless for a number of months after being kicked out of a hostel, the friend said.
On the day of his murder Oliver arrived at his friend's house at around 9pm and the pair walked to Church Road where they split up as the friend went to buy them some dinner and beers.
The friend said: “People have been saying I was lucky. He was staying with me because he had nowhere else to go.
"During the day he would travel to Oxford Street to beg. He was drinking too much and smoking weed but he wasn’t involved in gangs.”
He added: “I don’t know why, but something made me take that last picture of him the day before he died.”
The friend said Oliver had never known his father adding: “It seems like he never had a chance from day one. He could be difficult but he was a lovely guy who was just looking for somewhere to live. It doesn’t make sense.”
'He was an innocent bystander'
A court official confirmed Oliver had been due to appear at Willesden magistrate’s court on Thursday (March 10) accused of drunkenly attacking a man and damaging property on January 18.
Reports circulating on social media hours before the shooting warned that a feud between rappers over stolen jewellery was about to explode into bloodshed.
Mr Tetlow’s aunt, Kamilla Richards, 21, said: “He had nothing to do with it, he was an innocent bystander. The situation has nothing to do with him.”
The drive-by shooting is being treated by police as a “tragic case of mistaken identity”, Detective Chief Inspector Mark Lawson said.
People with information should contact police on 0208 358 0200 or Crimestoppers anonymously on 0800 555111.