Verse 32
This son of a murderer - Jehoram, the son of Ahab and Jezebel. But Ahab is called a murderer because of the murder of Naboth.
Shut the door - He was obliged to make use of this method for his personal safety, as the king was highly incensed.
The sound of his master's feet behind him? - That is, King Jehoram is following his messenger, that he may see him take off my head.