So, basically, he ran out of gas.
This is incredible. They could have topped up in Bogota, or even other airports, had they wanted to.
I have a couple of questions/observations.
(a) The co-pilot must have known what was happening. She would have recognized the danger as much as the pilot. But she was (i) young, (ii) the captain was also the co-owner/founder of the airline and (iii) in any event the Captain always has control of the plane.So she had no ability to overrule the pilot's decision to proceed to Medellin with insufficient fuel. I imagine she was upset. I think the cockpit voice recorder will have some very telling information.
(b) Why did the Captain not declare an emergency until the last moment? I think I know (all speculation, of course). Rules for aircraft require that planes carry a fuel reserve that allows them, in the evnt of an emergency, to reach their furthest alternative landing site PLUS thirty minutes extra fuel. By the rules, the LaMia jet should have easily been able to get to Bogota (it is less than an hour away by air). The Captain would have known these rules and knew that he had not complied. He knew he had taken off with insufficient reserve fuel. Had he declared an emergency he would have been exposed upon landing to an AeroCivil investigation and they would have discovered immediately that he had left short on fuel.
So, he deceived the Medellin Control Tower and said only that they were suffering a "Fuel problem" (sure was...he didn't have any!). He gave the Air Traffic Controller in Medellin no opportunity to give him a landing priority because he never told her what was really happening. When he finally owned up to the fact they were out of fuel, she gave him immediate priority but by then it was too late.
(c) The Colombian response was great. Apart from the attempt by air traffic to get the plane on the ground, the rescue personnel (volunteers, Red Cross, Firefighters, Police and others), the hospital and health care professionals, the investigators have excelled. Even the media, for a change, deserves credit in how they have covered this tragedy. Finally, of course, the response of the people of Medellin has been wonderful. The gathering at the football stadium last night was emotional, yet dignified. Mejor imposible.