Rapper K. Koke of Great Britain signed to the label in January and was said to be working on a new album titled Pure Koke Volume 2.
Transport police report that they took Koke; real name Kevin Georgiou, into custody after raiding his home.
Police believe the rapper shot a man in the back at Harlesden train station on March 9.
In addition to Koke a 16-year-old girl and 17-year-old boy have also been arrested.
Police are still searching for more leads in the case.