Daniel Gunderson is a police officer in Rockford, Illinois.
Daniel Gunderson, along with his partner Walter Kelly, arrived at the Roosevelt Asylum after Daniel told Walter the legend of the asylum they entered in order to search for teenagers who broke into it. The two then split up. After Daniel found the teenagers and accompanied them to the their car he drove away with Walter, who was behaving a bit strangely.
Walter committed suicide that night. Daniel went to a bar where he encountered Dean Winchester. Daniel didn't want to tell Dean anything about the incident since he was still mourning his friend, but Sam stepped in and pushed Dean aside and expressed concern for the police officer, who deserved some respect. Grateful, Daniel told Sam everything Sam wanted to know.