some additional details taken from here
Mozambique airline captain 'intentionally' crashed: probe
Abreu told a news conference that Dos Santos Fernandes locked himself inside the cockpit, ignored warning signals and did not allow his co-pilot back in moments before the Embraer 190 hit the ground.
"During these actions you can hear low and high-intensity alarm signals and repeated beating against the door with demands to come into the cockpit," he was quoted as saying by state news agency AIM.
The altitude was manually changed three times from 38,000 feet to 592 feet -- below ground level -- and the aircraft's speed was also changed manually, according to the preliminary report.
Airbrake parameters showed the spoilers, aerodynamic resistance plates on the wings, were deployed and held in that position until the end of the recordings, which proved the throttle was manually controlled.
"The plane fell with the pilot alert and the reasons which may have given rise to this behaviour are unknown. At the time, the co-pilot had left the cockpit and was absent while everything happened," said Abreu.