When is a practical joke not funny?

Went with a friend to visit someone I'll call Roy. He lived in an apartment in Montreal. We rang the bell and his voice came over the intercom. I put my jacket over my mouth and said, "Montreal Police Department. We have a warrant. Open the door please." When we got to the third floor, we knocked on his door. His jaw dropped when he saw it was us. In the background we could hear the sound of his toilet cistern refilling. He was speechless. We were sad. I still have the odd thought about Roy. And his toilet.