Shawn’s activism in the labour movement spans decades, when he first became a member of UFCW Local 416P while working as an electrician in the maintenance department at Robin Hood Multi-Foods in Port Colborne, Ontario, eventually becoming local union president. He also served as secretary-treasurer for UFCW Local 617P until its merger with Local 175 in the year 2000.
Following the merger, Shawn joined the staff as a union representative at Local 175. His subsequent roles in UFCW 175 included northwest regional director, executive assistant to the president and secretary-treasurer.
In 2007, Shawn was elected president of UFCW 175, which is the largest local union in Canada; he remained president of Local 175 for 17 years. He became a UFCW Canada national council vice president in 2007, and in 2019, he was elected UFCW International vice president.
In 2024, Shawn was elected UFCW Canada national president and UFCW International executive vice president, before becoming the UFCW International Secretary-Treasurer in May 2025.