(CNN) -- Here's what we know about Saturday's crash landing of Asiana Flight 214 and some of the key questions raised by those facts:
1. Based on the debris field, the aircraft appears to have struck the rock sea wall well before the start of the runway. There are some marks on the sea wall, consistent with an impact of some part of the plane. Some aircraft debris ended up in the water.
What we don't know: Did the flight crew simply land the aircraft short?
2. Passengers onboard the aircraft describe the engines spooling up and the nose tilting up just before impact, and a preliminary review of the flight data and cockpit voice recorders appear to show the pilots attempted to abort the landing 1.5 seconds before impact.
3. The debris field runs from the water, slightly right of the paved threshold and runway center, all the way to the stopped aircraft fuselage. The Boeing 777 lost its tail section, including vertical and horizontal stabilizers, near the end of the paved threshold, just before the start of the runway.
What we don't know: Is this an indication the tail of the aircraft detached after first impact?
4. What appears to be the Boeing 777's right engine is detached from the wing and wedged against the right side of the fuselage. Another engine is a considerable distance from the fuselage in a grassy area to the right of runway 28L. This appears to be the left engine.
What we don't know: When did the engines detach? Given the debris on the right side of the runway, could the engine off to the side actually be the right engine?
5. A preliminary reading of the flight data and voice data recorders show the 777 was traveling well below the target approach speed of 137 knots, the National Transportation Safety Board said.
6. Flight tracking records show that the Asiana 214 flight descended from cruising altitude much more steeply and rapidly than previous Asiana flights on the same route.
7. The instrument landing system approach on runway 28L was not working on the day of the crash. It had been down for some time. Flights were landing using visual flight rules. The weather was clear.
8. The runway's precision approach path indicator lights, showing correct flight approach altitudes, were working.
9. Most of the fire damage to the aircraft occurred after the 777 came to a stop on its belly.
10. Passengers described the cabin interior as heavily damaged, with overhead bins dropping and at least one life raft/escape slide inflating inside the aircraft, trapping a flight attendant, who was freed by passengers.
11. Audio recordings of air traffic control conversations show the pilot did not declare an emergency before the crash landing. Emergency vehicles were dispatched afterward.
12. The aircraft was built in 2006 and was purchased new by Asiana.
13. All four pilots on the plane have been interviewed by U.S. and South Korean investigators, the head of South Korea's Aviation Policy Bureau said.
What we don't know: What did the pilots say about the speed, altitude and other factors before the landing? Choi Jeong-ho, the head of the aviation bureau, said he could not release details pending the investigation, which he said will continue for at least a week.
14. The San Francisco Fire Department said one of the victims killed may have been struck by an emergency vehicle, San Mateo County Coroner Robert Foucrault said. Asiana has identified the two deceased passengers as Ye Mengyuan and Wang Linjia of China. Both were 16.
What we don't know: Which teen girl may have been struck by an emergency vehicle? And did the girl die from the plane crash or from the vehicle? Foucrault said his office is trying to determine the cause of death.
CNN's Chelsea J. Carter, Richard Quest and Miguel Marquez contributed to this report.