McGrath has said previously that the investigation team believes the killers lured Sam Rimmer’s friends out of a property by making some kind of noise.
At least eight shots were fired towards the group, one of which struck him in the back and exited through his chest.
While no-one else was injured, some of the other bullets struck residential houses.
The weapon was established to be a Skorpion sub-machine gun, a Czech-made weapon capable of firing repeated shots in a fraction of a second.
McGrath said: “Sam’s family and friends will miss him every day, but special occasions such as birthdays will always be particularly difficult and we will certainly be thinking of them today on what would have been Sam’s 26th birthday.
“Let me be clear, the investigation into Sam’s murder is ongoing and we remain determined to find the people responsible.”