What type of irony does "The Ransom of Red Chief" end with?

The story, "The Ransom of Red Chief," exemplifies situational irony where the results contradict what is expected. The story ended with the kidnappers paying the ransom to the victim and taking off in fear instead of instilling fear and taking the ransom as expected in such situations.

Sam and Bill kidnap Mr. Dorset’s son, Johnny alias the Red Chief. They make it to their hiding place in the mountains. However, the situation changes when Sam leaves Johnny with Bill. Johnny terrorizes Bill in Sam’s absence. The kidnappers fail to contain the boy who is in charge of the situation and disinterested in returning home. Sam sends mail to Mr. Dorset requesting for ransom, but instead, Mr. Dorset responds with his own ransom demand of $250. The boy is relentless and finally the kidnappers yield to Mr. Dorset’s demands and pay him the ransom so he could take back his son.