2004 Lexus RX 330 cut off after jumpstart

I own a Lexus RX330 2004 and I left the light on the car, but my roadside assistance tried to jump it just now and the front lights started flickering and I got in the car and pressed the accelerator and the car cut off. He’s saying it’s the alternator. What do you think? I’m looking for the “car community” where I could ask questions but I can’t find it here. It’s been about 1 year since I’ve been on this site.

The alternator may have failed, you will need to have the vehicle towed to a shop and have the battery and charging system tested.