His family revealed the news via the following statement from his GoFundMe page:
Maxwell was 66 years of age at the time of his passing and had been fighting the most difficult battle of his life against lung cancer. Unfortunately, the cancer had spread throughout his body and his fight ended on Sunday. Maxwell's family has set up a GoFundMe to help cover the out-of-pocket expenses involved in the treatment that Maxwell was undergoing.
Maxwell played 612 games with the North Stars, Nordiques, Maple Leafs and Rangers. In his career he scored 98 goals and 368 points. His only season on the blueline in Toronto came in 1985-86, when he played 52 games for the Leafs, racking up 8 goals and adding 18 assists for a total of 26 points.
RIP to Maxy and our most sincere condolences to his family as they continue to mourn his loss.