
Some believe it is a paramedic. But, why in the heat of June, would one of the paramedics wear a long sleeve shirt? The others are wearing short sleeves. Some thought it could be Paris, but she would be much shorter. In fact, I did some side by side comparisons of "gate man" with some other photos and came up with some interesting results.
Whoever "gate man" is, they have the same proportions as someone else we recognize...
First here is a comparison of "gate man"'s shoulders and arm. :

The shoulders and the arm length proportions appear to be a match.
But let's do more of a "full body" comparison. Side by side below is a body comparison, and the head, shoulders, elbows, knees, and feet match.

This shows that the individual behind the gates is too tall to be one of the children. In addition, this person coincidentally mirrors MJ's proportions.
So who is this mystery person? Whomever they are, they may be able to moonlight as an MJ impersonator - they already have the ponytail. :)