[luncheonmeat]

When he told his daughter that his legs were tired and "Bo Khui", it could mean he was breathless or the stairwell door was not open. So it looks like he was too weak to move out and trapped there till he died of hunger.

People. especially those with weak legs will generally take the escalator or lift. Why would he walk to the stairwell which is out of the way. Could be foul play... unless he just fainted while passing that area.