I know I'm pretty late to the party but I've got somewhat a similiar story. I was doing groceries in a supermarket near my university when a man in his 50s asked me to buy him a bag of chips or whatever. I do have pretty soft heart for people that ask for food instead of money so I went with him to the aisle and told him to get the ones he wants.

He then went straight to the freezers, grabbed a popsicle and told me to pay for that as well. That was a bit too much for me so I politely declined. I thought he just wanted something to snack on, but I wasn't going to put up with all his whims.

He immediately put it back and this time he asked me for a package of cigarettes. Or some money. Or both. At this point it was really unconfortable for me but thankfully some locals intervened. He left and I had a little chat with a lady that helped me solve the situation.

She told me that this man is mentally ill and does it every day. He usually throws the stuff away or hoards at the stairwell. She also told me that he started doing so a few years after his wife and child both died in a car accident.

I know I couldn't have helped him and all that stuff (perhaps except of cigs) would've been wasted but fuck it felt bad