Some dude was staring at my Mom's ...?

I am a 16-year old guy. My mom is in her 30s. She is good looking and in good shape. She isn't fator ugly or anything but sometimes she wears some revealing outfits. This morning I went with her to the apartment laundry room. She was wearing this sleeveless shirt. As she was putting the clothes in, she had to bend down a bit and her s were all jiggling. This guy comes in and he uses the washing machine right next my mom's and he pretty much had his face in her ! What's up with this guy? I know she wasn't wearing a bra and so her were visible. So should I tell my mom or what? What about my dad?