He's lying! Don't fall for it. Everything you say can and will be held against you. Be careful.
He asks you some questions that make it clear you're being accused of doing something wrong. Maybe it's stealing from the company. Maybe just punching in wrong. Maybe giving unauthorized discounts. Maybe a violation of some policy. He says he's trying to help you, so you tell him everything. Yes, you did use a plastic spoon from the deli and didn't pay for it. Yes, your boss gave you a candy bar and said it was going to be destroyed anyhow, so you took it and ate it. Yes, you used your employee discount to buy something for your best friend. Yes, you forgot to punch in, so you went in and wrote down your best estimate of the time you came in.
That wasn't very careful, was it? You've just confessed to doing something wrong. Maybe even a crime. But he's so nice. He tells you the only way you can save your job is to write down everything he tells you to write.
He's really lying now. Say no! Tell him that you will be glad to write your own statement in your own words, and tell him you'll provide it to him the next day. If he says you need to write what he says or be fired, you're already gone. Don't believe him for one teeny, tiny second.
He tells you to write down what you did, only the way he puts it sure makes it sound worse than it was. He conveniently leaves out how your boss told you to do it or said it was okay. He leaves out how others of, say a different race or sex, do it all the time and suffer no consequences. He has you write down that you understand you violated company policy. Maybe he even has you write down that you agree to pay the company some amount of money. Then he tells you to sign it.
Tell him to pound sand. Do not do this. If you do it, you're fired, and possibly arrested.
Let's say you believe this guy and write it all down. What's going to happen next? He grabs it, maybe leaves the room for a couple minutes, then tells you that you're fired. You're escorted out like a criminal.
If you are called into a meeting with Loss Prevention, that's a meeting where you need to be very aware that you are being accused of doing something wrong and you're probably being fired. They are not your friend. When in doubt, tell them you want to leave and speak to an attorney. Yes, they can fire you for leaving, but that's way better than admitting to something you didn't do, or admitting to a crime. You can always write up your response to the accusations calmly after you've had a chance to think straight later and send them to HR.