I believe Kyron was taken by someone he may have known at the school. Or there is a possibility that it was a stranger but someone that Kyron thought belonged there and was harmless. Such as if the person told them they had a child there in a different grade or someone who ask Kyron to help him with something.
When I have watched Oprah's shows on stranger abductions the MO was basically the same thing. The person who pretended to be the predator would walk up to the child and ask for their help and much to the parents horror the child just took the hand of the person and walked off with them.
I think Kyron would think that a bad stranger would be someone that looked like the boogeyman or boogeywomen. Scary. Someone he may have to fear trying to nab him from his house or his own yard but at his age with his cognitive thinking I don't believe he would see any danger from those that were inside his own school.
I think Kyron had been brought up to respect adults and had no circumstances where he had to fear one so imo he saw adults as kind people.
Imo, whomever did this saw Kyron and his mom there and he saw Kyron's mom leave. I think he struck when the opportunity arose shortly after Kyron left to go back to his classroom.
Imo, it is likely this person stopped to chat with Kyron a second as Kyron was going to his classroom, bragging on his exhibit, and telling him he really needed to go see the electric exhibit. He may have told him the electric exhibit was downstairs and the perp was waiting at the bottom of the stairs when Kyron came back down after talking with Tanner and told Kyron he needed his help first and needed to bring something inside from his vehicle. So they went out the exit door closest to Kyron's room.
"Pardon Our Noise, It's the Sound of Freedom" USMC New River Air Station, Jacksonville, North Carolina