Jim, his friend was 18-year-old Abdul Wahab Hafidah.
My ITV link identified the gangs involved,
"A feud between two south Manchester gangs is behind the outbreak of violence in Moss Side which has resulted in two murders since December, police believe. Tensions between teenage members of the Moss Side Bloods - an offshoot of the infamous Doddington crew - and the Rusholme Crips have erupted over the last few months, according to a senior police source. "
Give your sources that those gangs were involved and for their makeup.

The friend was a gang member and his killing was part of a gang feud and not racist.
ITV link I provided.
"are being linked to the feud. Abdul Wahab Hafidah, 18, was run over by a Vauxhall Corsa on Moss Lane East during the evening rush-hour before the occupants stabbed him in his neck and abdomen on May 12."
http://www.itv.com/news/granada/2016-05-25/gang-feud-behind-outbreak-of-violence-in-manchester/

From your own link Jim,
"A family friend also alleged that it was the murder of Abedi's teenage friend that caused him to kill.
The teenager was run over and stabbed in Manchester in May 2016 in what is believed to have been a gangland killing.
http://www.dailymail.co.uk/news/article-4539734/Sister-reveals-motives-Manchester-bomber.html#ixzz4kGXf6D46

MSM link I provided.
"Such anger was reportedly heightened when one of his(Abedi's) friends, 18-year-old Abdul Wahab Hafidah, was murdered in the Moss Side area of Manchester a year ago."
http://www.msn.com/en-gb/news/world/salman-abedi-young-man-thirsting-for-revenge/ar-BBBxoOp