He's using Rithmic, which is my preferred broker for prop firms because you have many ways to control risk available to you.
NinjaTrader can auto close positions but I prefer a broker-based solution that doesn't depend on:
- NinjaTrader running
- NinjaTrader not losing it's connection
- You computer not having any issues
- Your internet not having any problems
This ensures that you will never have open positions or orders after the time you set.
Here's a short video showing how to set these up in NinjaTrader and Rithmic R Trader Pro.
NOTE: I setup both methods so I'll never have to worry about failing an account because of not closing my positions.