The following is based on limited witness accounts, inspirations for the cover stories, and credible accounts prior to the second news article discrediting the first -

A moon crescent shaped craft, travelling at high speed collided with a mogul weather balloon, (first debris field) this threw the craft into a spin, causing it to contact with ground, it was moving with enough speed to “skip” (second debris field and score marks in ground) and regain the air briefly before hitting the ground a second time, and sliding into its final resting place in a raised area of terrain. (Not much detail on the raised area - either a natural rise in the terrain, or a pile of dirt pushed up by the craft)

It is reported it contained several crew or passengers, (undefined qty) of unusual appearence. Several had been critically or fatally injured in the crash, however at least 2 survivers, the size suggesting they were children, were found a short distance from the wreck around what was later thought to be a rescue beacon or similar device of value. Because of their unusual appearance and because they refused to move away from the device after several verbal warnings, one of them were shot (undefined if it was fatally) the second ran at this point and was captured.

What happened to the survivers is ultimately unknown, the last bread crumb suggests the bodies and survivers were taken to a hospital under military supervision, where a nurse reported accidentally spotting one of them, before they were loaded in a vehicle and transported to an unknown destination.

It is thought it was loaded and trucked to a secure military base. The area along the crash course was searched in great detail to locate all fragments, and any fragments of the mogul balloon found was taken and showed to reporters as the cover story. Given the craft was spinning quite a lot, is is possible small fragments may have been spun and thrown out of the immediate search area, but it is unclear if any privately held fragments still remain.

1. The crew of the craft were aliens.
2. Another possibility is they were members of the Vima/Vedic race, who are generally considered to have achieved space capability during the last technological rise of civilisation 10,000 to 15,000+ years ago. Sightings of vedic like crafts have been reported as far back as Alexander the Great, and by remote farmers in the early 1900's prior to the wider adoption of aircrafts.
3. The most likely is they were Germans flying so called “foo fighters” from the Maud land NAZI Aerospace research and Submarine base located near hotsprings under a glacier in Antartica and the target of operation highjump and operation paperclip; which is why the entire incident was immediately classified and covered up with such enthusiasm.