The actor was diagnosed with cancer in 2016 and had surgery that appeared to help his recovery. By March 2018, however, he’d been diagnosed with inoperable cancer.
"It's not until they tell you you're going to die soon that you realize how short life is. Time is the most valuable thing in life because it never comes back,” he said in a statement in March. “And whether you spend it in the arms of a loved one or alone in a prison cell, life is what you make of it. Dream big."
Stefansson is survived by his wife, Icelandic actress, Steinunn Ólína Þorsteinsdóttir, and four children.