A day after Kenyans celebrated David Rudisha's stunning world record victory in the Olympic 800 metres, they were brought back to earth as Kisorio's confession and accusations cast a shadow over one of the sport's powerhouses.
Kisorio, a former African junior champion in the 5,000 and 10,000m who had hoped to make the Olympic team, returned a positive test for an anabolic steroid after the Kenyan championships in June where he raced in the 10,000.
"We suspended him provisionally pending further investigations," David Okeyo, Secretary General of Athletics Kenya, told Reuters of Kisorio, who finished 10th in the Boston marathon this year.
"We don't joke with doping matters. This year alone, we have banned four athletes. We have even involved the relevant arms of the government in our investigations.
"Any athlete who tested positive, whether in Kenya or abroad, was sanctioned after investigations.
"We spoke to Kisorio at length and he gave us very useful information, which we handed over to the government agencies.
"We had not concluded investigations (into Kisorio's case) by the time the Olympics was starting, but we shall go to the bottom of the matter when we return home."
Okeyo said the timing of Kisorio's confession was to portray a "negative" picture of Kenyan athletes.
"We refuse to buy that negativity and pay tribute to our athletes who have done us proud," he added. "I congratulate David Rudisha on a job well done on Thursday."
Kisorio gave a long and detailed description of his blood-doping and steroid regime, blaming medical staff behind the system and claiming many fellow Kenyans were using illegal performance-enhancing procedures.
"I didn't run up to my standard during this year's Boston marathon," he told German TV channel ARD.
"To get my power of endurance up, he (a doctor) told me they will take care of it. I asked if this is considered doping. He said: 'No problem. The substance stays only three to four days in your blood circulation and then it is impossible to prove.'
"I went with it, because everyone told me, I wasn't the only one - and none of the others got caught for doping.
"I know that a lot of medical substances are used, which are injected straight to the blood for the body to have more oxygen. And when you run, you run so smooth. You have more stamina.
"When the prize money comes in the doctors want a piece of your success," Kisorio added.
"There are some doctors who settle down in popular athlete areas where you can find the training camps. These men just open a pharmacy and claim they are just selling legal medication. Then they approach the athletes. It is the same all over the country.
"Athletics Kenya knows now what the situation is like. Maybe this is an ongoing problem that finally surfaces."
- David Rudisha