An app is not responding in one of the pane of my tmux session. It does not respond to any Ctl-C and I forgot what the process is it.

So I did the following to identify the process:

    $ tmux list-panes -s -F "#{pane_pid} #{pane_current_command}"
    1896 tmux
    1899 ssh
    $ pstree 1899  # Problem at the lower pane
    -+= 01899 antkong -zsh
     \--= 65662 antkong ssh -i prod.pem ubuntu@localhost -p 2222

Then run kill -9 1899 to kill it