There are a number of reasons Kayerts hangs himself at the end of the story. Previously, he shoots Carlier mistakenly after they have been arguing about the sugar. Kayerts feels lethal ill (p. 33, l. 64) shortly after killing his assistant and only pal at the trading station. Afterwards, Makola appears and talks with Kayerts. Makola gets to the conclusion that Carlier “died of fever” (p. 34, l. 21) and Kayerts simply stays silent. Kayerts might have killed himself due to the fact that he feels alone, which ends up being most apparent on page 34, ll.
6-28.
His only ‘friend’ he might talk to is dead. Furthermore, he shot an unarmed partner and might be afraid of being apprehended. (which is not in the text …) He lost his buddy and partner and can’t continue life without him. Besides, he feels guilty because he accepted the selling of the slaves, which is– naturally– forbidden. (p. 25, ll. 55-64) This might be one factor, why Kayerts didn’t see another possibility to get rid of all his issues than hanging himself.
Another substantial point is his daughter Melie.
He cannot come across Melie because he would disappoint her by his own failure. Furthermore, Kayerts seems to understand that colonialism is all about exploitation (p. 36, ll. 3-7; p. 34, ll. 37-2) Makola had said that “Carlier died of fever”, which was a lie. Kayerts does not want to lie. He cannot live with this lie because of his bad conscience. This despair can be found on page 34 ll. 28-36 and p.
35 l. 64 when he prays to god. From these lines we can infer that Kayerts thinks about human life, which has no sense for him (p. 34 ll. 0/31) At the very end of the story, the steamer is arriving at the station.
Kayerts is probably nervous and afraid of his director because Kayerts and Carlier failed. He has possibly no choice and does not see a point in living. As far as I am concerned, all those reasons are brought into contact and explain why he hangs himself. There is not only one reason for committing suicide. Of course, there are more important and less important factors, but all these lead to his suicide. To my mind the main point is that Kayerts has nobody who helps him to get out of this situation.