Tul Prasad Sherchan, who claims to have been groomed from the age of five years to head the covert operations of Nepal's Royal Bureau of Intelligence - akin to American agency CIA and India's RAW, created a sensation Wednesday when he walked into Nepal's best known media club and said he had planned the killings in 1975.
While the claim was greeted with disbelief as well as derision, police, however, moved swiftly, arresting him near midnight Thursday while he was heading towards his 'shelter'.
Minutes before his arrest, Sherchan gave an exclusive interview to IANS, detailing his background and motive.
It is an incredible story that lays the blame on the slain royal family's 'greed' and tendency to 'suck the nation dry' by siphoning off all the foreign aid Nepal received from donors.
"I went to London in 1973 for intelligence training," Sherchan told IANS.
"At that time, Birendra's younger brother Dhirendra and his wife Prekshya were in London. I met the prince and warned him that if the royal family did not mend its ways, it would be eliminated."
According to Sherchan, Dhirendra - who too was slain in the carnage in the Narayanhity royal palace June 1, 2001 - promised to convey the warning to his elder brothers but the palace dismissed it and instead, tried to muzzle Sherchan when he returned to Nepal.
The royal family, who were also omnipotent at that time, implicated him in a graft charge and got him imprisoned in Kathmandu Valley's Nakhu Jail for 40 months, he claimed.
It was during his stint behind bars that the massacre occurred.
"On June 1, 2001, I told seven people - including the jailor and jailed (former) Maoist leader Matrika Prasad Yadav that by 9 pm that day, the royal family would be eliminated," Sherchan said.
The self-admitted assassin said he, however, decided to spare Birendra's second brother Gyanendra, who went on to become the next king.
"Our other goal was to retrieve the money the royals had stashed away in banks abroad," he claimed. "That would not have been possible without any survivor."
Sherchan said he chose Gyanendra because the latter would be easy to deal with. Gyanendra was a businessmen and 'understood about finances' and during the king's absence from the kingdom, acted as regent, being well-versed in politics and statecraft.
While Gyanendra was absent from the family dinner that turned fatal that night, his wife Komal and son Paras were present. However, they escaped while the king, queen Aishwarya, their three children, Dhirendra and four others were gunned down.
"We decided not to hurt Gyanendra's wife and son as we did not want to give him any shock," Sherchan claimed.
The man who admitted to regicide said many people knew he was behind the killings, including Gyanendra, the then prime minister Girija Prasad Koirala and the opposition Maoist party. He also claimed he had given several interviews to magazines claiming responsibility but no one did anything.
"Dipendra is innocent," Sherchan said, absolving the crown prince who has been blamed for the massacre in a fit of drug-bolstered anger with his parents. "So are Gyanendra, the CIA and RAW."
There were several theories after the assassination, blaming Gyanendra and foreign governments like India and the US.
Sherchan also said that his investigations show the slain royals' hidden wealth is concentrated in Switzerland and India.
He, however, refused to name the people who, according to him, had actually pulled the trigger inside the palace that Friday. However, he said that he had tapes to corroborate his claims.
He also said his name, though unknown in Nepal because of the secrecy his job required, was known to the CIA, RAW and ISI.
Police Superintendent Nabaraj Silwal said Sherchan would be examined to determine if he was sane.
However, the eloquent man, who was moving with his media advisor and two bodyguards in tow, was lucid and coherent.
A senior journalist, who did not want to be named, said it could be an attempt by the real culprits to serve up a scapegoat.
"With a succession of governments saying they would investigate afresh the palace killings, the culprits are getting jittery," he said.
"When rich landlords run over a man, they pay their drivers to take the blame. This is the same syndrome."