RALEIGH, N.C. — A series of threatening letters, some warning of anthrax, are turning up around Raleigh. Investigators said they are coming from an unusual source -- an inmate at a youth prison.

The state and the U.S. Secret Service are investigating Cornelius Tucker. Tucker may have sent letters to the president of the United States and his daughter.

One of the letters was sent Wednesday night to a missionary at North Ridge Church in Raleigh.

"It threatened that they were going to do a drive-by shooting on a lady, kidnap her grandchildren, that there were explosives in her car," said the Rev. Jeff Singfiel of North Ridge Church.

"If it turns out that he is the one that actually sent the letter, and it wasn't just somebody using his name, then we have to, as usual, look at our policy and see if we're doing everything we can to prevent something like that," said Pam Walker of the Department of Correction.

Raleigh police said Tucker sent at least seven threatening letters to people this week.