I have two theories
Theories
So it seems like the girls didn’t scream as none of the witnesses mentioned anything about hearing a scream, and it seems like they managed to put everything they bought into the car before the kidnapping. It’s impossible to kidnap three people at once, which is why I believe the kidnapper had two other people to help him which would mean they could all grab the girls and cover their mouths which means no screaming would have been heard.
It’s suspicious to me that one of the witnesses mentioned to only see one girl when the other two witnesses claimed that three girls were taken which it could be a bit of a stretch, but he could have been involved in the kidnapping.
Another thing to mention is that the kidnapper (s) probably came from behind with their vehicle parked close to their car that way as soon as the girls left from putting the presents in the car, and started to walk back to the mall. The kidnapper (s) could just grab them from behind and put them into the van and they would never be seen again as well as there would be no evidence left behind, so I have no idea on who the kidnapper was, but I assume that the kidnapper told the girl what to write on the letter so it would have her handwriting, as well as the kidnapper would not have finger prints on the letter. I assume the girl was then forced to say her address so they letter could be sent out.