The built-in kill switch automatically kills program should you get disconnected from the VPN.
To setup the Kill Switch in MacSentry first click on the settings button from the main screen of MacSentry.
Then click on the Kill on Disconnect field to bring up the Kill Switch app selection panel.
Then select the program(s) you wish to be killed when you disconnect from the VPN.
You'll notice the apps start appear next to "Kill on disconnect" as you select them as well as turn red in the Kill Switch app selection panel.
To remove an app from the Kill Switch simply click it again to remove it from the list.
Once you are done click the X in the top right of the Kill Switch Application activation window and then click Close in the Settings window.