Seoul, South Korea (CNN) Mr. Park shifts uncomfortably in his seat. As one of the most senior North Korean officials to ever defect, he was preparing to tell the ugly truth about the regime he served faithfully for decades.
This is not his real name; he wants his identity hidden for fear of retribution against friends and family still in Pyongyang. It's not surprising when you hear what he has to say.
His first allegation is shocking. He claims North Korean leader Kim Jong Un ordered his own aunt, a blood relative, to be poisoned.
"On May 5th or 6th of last year," says Park. "Kim Jong Un ordered his aunt, Kim Kyong Hui, to be killed. Only his bodyguard unit, Unit 974, knew this -- now senior officials also know she was poisoned."
Park says Kim Jong Un wanted to silence his aunt, who complained angrily for months after her husband and presumed No.2 in the country, Jang Song Thaek, was killed in December 2013.
The fate of Kim Kyong Hui has been the subject of intense speculation since she disappeared from public view in September 2013, a few months before her husband's death.
Various reports have suggested that she had a fatal stroke, heart attack, committed suicide or was in a vegetative state after undergoing surgery for a brain tumor. In February, it emerged in parliament that the South Korean intelligence agency believed she was still alive.
South Korea's national intelligence service has also claimed that, since coming to power, Kim has executed his enemies, killing at least 15 senior officials so far this year.
CNN put the allegation to a high-ranking member of North Korea's inner circle during a rare visit to Pyongyang last week.
"Malicious slander!" replied Park Yong Chol, the deputy director of the DPRK Institute for Research into National Reunification.
"Especially because they tried to link the alleged statement to the august name of our Supreme Leader Marshall Kim Jong Un," he added.
But he did not deny that executions take place here of those who try to overthrow the government or subvert the system. "It is very normal for any country to go after hostile elements and punish them and execute them."
Jang and his wife had been tasked with guiding the young leader through his early years of power after the death of former leader, Kim Jong Il. But Park says the leader and his uncle did not see eye to eye on money.
"After a year and a half, Kim Jong Un wanted to build the Masikryong Ski Resort and Munsu Water Park, basing it on his experience in Switzerland. Jang Song Thaek initially agreed ... but suggested building the economy first. That is where the friction began."
According to Park, Jang was arrested, tried and executed in less than a week. "Jang was not executed publicly but in an underground secret room. Nobody said they witnessed the execution of Jang," says Park. But he claims up to 30 of his and his wife's aides were killed far more publicly, some by firing squad, not using an ordinary gun, but four-barrel machine guns.
Kim Jong Un publicly called his uncle "scum," claiming he had been working against the government and trying to topple the regime. Park says he worked closely with Jang Song Taek and these accusations were simply not true.
Much of what Park tells us cannot be independently confirmed, North Korea is one of the most closed and repressive countries on earth.
Park paints Kim Jong Un as a brutal dictator whose actions have shocked those in and outside North Korea. An elite accustomed to purges and executions has been shaken by Kim Jong Un's willingness to kill even family members if they dare to disagree.