Disclaimer: Hellkite is an open project where anyone can create evidence for this new cryptid. Evidence posted here has been made at least partially by me, but more can be found here, as well as instructions to participate.
First appearance of Hellkite in the media:
First time the Hellkite is allegedly captured on camera, 1938. Stories about it had been spreading in Iowa for some months before that. Some compare it to the Otaktay, a local Sioux myth. Critics claimed it was just a kite made by kids to scare the local parishioners.
The Mexico Sighting
Mexico, 1911. During the Mexican Revolution, a group of soldiers under General Pascual Orozco finds an unusual carcass on their way to Ciudad Juárez. They gather to take a picture with it before continuing.
Gerardo García Temprano, one of the officers in the group, keeps a notebook where he appears to still be curious about the creature. Over the next few days he would make multiple drawings of it, imagining its live appearance. We do not have any more information about the author, but we can surmise he attempted to desert the army shortly after writing the last entry.
The Thermal Image
In 2017 a group of cryptid hunters go out to find the Hellkite in the Lagodekhi forest (Georgia) after local newspapers mention sightings of a similar creature. They bring a thermal camera to see through its camouflage. Upon returning they noticed these among their pictures.
First appearance: Library of Congress, The Redwood Gazette, Pixabay.
Mexican Sighting: @wifi_failure provided the drawings and @EyesJar found the text. Image sources: LoC, Pixabay, Needpix, PxFuel, and Tomás Castelazo, Andrew Mercer, Ryan Baumann and Museum of Veterinary Anatomy FMVZ USP on Wikimedia
Thermal Image: Giorgimailo (wikimedia)