The schoolboy from the northeastern town of Ahtme accused the president of the Sept. 11 terror attacks against the World Trade Center and the Pentagon, the newspaper Postimees reported on Oct. 2.
U.S. law enforcement bodies informed Estonian security police of the threatening letter, which was five lines long and was signed "Your Death."
The student said he did not imagine the letter would go beyond his school's server.
Two days after U.S. authorities established from the Internet address that the letter came from Estonia the boy admitted his act to security police.
The letter ruined the boys' chances of taking part in an international competition in mathematics in the United States. His parents may be fined.
But the head of the boy's school had only good words for him, saying he was well-behaved and one of the best students in the school.
The boy himself said he sincerely regretted his act.
In the same week a Lithuanian man was imprisoned in the United States after making a similar non-serious threat. The man will most likely have to leave the country after joking about hijacking a plane and crashing it into Chicago's Sears Tower, Lietuvos Rytas reported on Oct. 2.
The newspaper said that 23-year-old Liutauras Padalevicius ran into trouble during a party at a nightclub in Omaha, Nebraska, last week.
Padalevicius, a Chicago-based vacuum cleaner salesman, went to the nightclub with three friends on the eve of his flight back to Chicago from a vacation in Omaha.
According to Lietuvos Rytas, staff at the night club heard the inebriated Padalevicius talking about his hijacking plans and immediately called local police, who have been more sensitive about terrorist threats following the Sept. 11 attacks.
Police officers soon arrived at the nightclub, detained the Lithuanian and took him to Omaha police station for interrogation by both local authorities and the FBI. Padalevicius was later placed in custody at Douglas County Jail.
The next day Douglas County prosecutors announced no criminal charges would be pressed due to a lack of evidence. Another officer was quoted as saying that the statements resulted from his having drunk too much.
But ever since the Federal Immigration and Naturalization Service took an interest in the case Padalevicius has been detained in prison in the Midwest, charged with failing to leave the country on the expiration of his residence permit.