Officials found the 11-year-old and Byrns at a Holiday Inn Express in Macon, Ga., after tracking the girl's phone.
The search for an "endangered" Florida girl ended at a Macon motel Sunday.
Byrns will face charges of kidnapping a child under 13 years old and could face more as the investigation continues, Demings said.
Anyone with information on her whereabouts is asked to call the Orange County Sheriff's Office at 407-836-4357 or contact 911.
Police said Byrns initially made contact with the girl through an online video game platform, where he posed as a young girl.
Johnson disappeared sometime after 10 p.m. the night before from her East Orange County home.
Johnson's parents said they were aware their daughter was talking to an individual from IL, but did not know she was in danger at the time. Authorities say she might be carrying a blue and white striped backpack.
"In this case, this individual on the other end (was an) adult male who is a child sexual predator and that's all of our worst nightmares", police said. She was with Byrns, but police would not go into detail about what went on between the two while they were together.
"She's lucky to be alive", Demings said at a press conference Monday.
Neighbors say Byrns lives there with his mom and dad. "He may be charged with additional charges", said Sheriff Demings.