Q: Vehicle shutting off after a loud squeal.

Based on your description I believe you could be having one of two things happening. One explanation of your squealing noise could be a slipping serpentine belt. This belt drives all the accessories attached to your engine such as your power steering, air conditioning, and water pump. If this belt is squealing this means that it is slipping and not driving the accessories. If the belt isn’t turning your alternator and your battery will run down and the car will shut off. The next possible cause for a squealing noise is a vacuum leak. In some cases a vacuum leak can sound like a squeal depending on how and what the air is being sucked through. If you have a vacuum leak in your engine the air/fuel ratio can get messed up and cause it to run very poorly and in some cases stall out. I would ask for help from a mechanic to check your engine over and find the cause of your squealing and stalling issue.