The white guy on the video concerns me the most, as others have stated here as well. When he is initially walking, you can see him turn back and look toward Hannah and the people behind her. Now either something caught his attention (like the group of boys hassling Hannah or something) or he was checking to see where she was in relation to him. When he dips into that cove, he seems to pull out his cellphone and look at it just as the other lone male walks by and then immediately puts it away once the lone male passes and Hannah walks by, he falls right in line behind her and in front of the group of boys. Now, if I'm a good citizen, and I am concerned about a stranger's well-being, I'm not sure I would follow her, but rather stop her and say something to her to make sure she is ok. If he was following her to ensure she did not get hassled by anyone and wanted to keep his distance before intervening if necessary, he could've caught up to her and walked with her before the group of boys caught up to her.