The T2 Trainspotting star and former boxer died following a shooting near his home in Edinburgh, Scotland, on April 17. He was 42.
Welsh appeared as the kingpin Doyle in Danny Boyle's 2017 sequel to his classic 1996 film Trainspotting. It was his first professional acting role.
He also ran charity projects for young adults in the city to help them stay fit and out of trouble through his Holyrood Boxing Gym, according to Edinburgh Live. "His death is being treated as suspicious and inquiries are continuing," the Edinburgh Police Divison shared in a statement on Facebook.