Two cats and an angry teenager

Saw both Pixie and Maomao tonight. Fed Pixie two Whiskas wet packs - she has very good appetite! Pixie is wearing a collar with a bell but without the safety buckle so I'm a little concerned. I may want to have her collar changed but am uncertain if she is "owned" by someone. I don't like the idea of the bell for a stray (assuming she is one). Anyway, towards the end of the feeding session, I saw this guy, a teenager about 13-15 years old (I think), in some uniform (McDonalds??) kicking the wall, looking frustrated and angry. Worried that he may take his anger out on the cats, I decided to loiter for a while more (my digicam and mobile was with me, just in case I need evidence!). Soon after, he disappeared. I will check on them tomorrow. He better not do anything funny!