What event made a change in Zaroff's character?

Zaroff's altercation with the Cape Buffalo, and his subsequent hunting of jaguars changed his thinking about the hunt.

"After the debacle in Russia I left the country, for it was imprudent for an officer of the Czar to stay there. Many noble Russians lost everything. I, luckily, had invested heavily in American securities, so I shall never have to open a tearoom in Monte Carlo or drive a taxi in Paris. Naturally, I continued to hunt--grizzliest in your Rockies, crocodiles in the Ganges, rhinoceroses in East Africa. It was in Africa that the Cape buffalo hit me and laid me up for six months. As soon as I recovered I started for the Amazon to hunt jaguars, for I had heard they were unusually cunning. They weren't." The Cossack sighed. "They were no match at all for a hunter with his wits about him, and a high-powered rifle. I was bitterly disappointed. I was lying in my tent with a splitting headache one night when a terrible thought pushed its way into my mind. Hunting was beginning to bore me! And hunting, remember, had been my life. I have heard that in America businessmen often go to pieces when they give up the business that has been their life."