Northeastern police chief Joe Griffin said yesterday that Womack had sent four similarly threatening letters to the Northeastern police beginning in April of this year.

One letter claimed responsibility for a fire on campus; another threatened harm to several police officers. The others contained bomb threats, Griffin said.

"We are very delighted to have the individual in custody and that he is being held without bail because of the threat he posed to students," Griffin said.

Several hundred thousand dollars worth of books from the Northeastern University libraries were also found at Womack's home in Arlington. Police and FBI agents executed a search warrant there Wednesday.

Griffin said Womack was a part-time student at Northeastern when he was stopped by campus security guards last month for trying to leave the library with several books he did not check out.

Authorities said they found a cache of books, manuscripts, typewriters, photography equipment, cutting implements and other objects allegedly stolen from the University in Womack's Arlington home.

Johnson and Rooney, who spent much of yesterday fielding interview requests from local television and radio stations, as well as area newspapers, stressed the "tremendous amount of damage" Womack caused.

Harvard police said Womack had been photographing the pages he tore out of the books onto microfilm and then throwing the sliced pages into the trash.

Rooney said authorities recovered more than 300 rolls of microfilm, each of which contained at least 15 full texts.

Womack, who was employed for 18 months between 1990 and 1992 as a part-time book shelver in the stacks at Widener, used a knife and his hands to rip out the pages from books, including many on church history, literature and organic chemistry.

Johnson said Womack had been on the department's "short list" of the 20 most wanted suspects as early as 1991. Police said they had initially suspected that the perpetrator was a library employee because he was able to elude monitoring devices and was never seen exiting the library with stolen items.

"He was on our list, but it wasn't possible to narrow it down any further," Johnson said. "And then the slashings stopped."

University Librarian Sidney Verba '53 yesterday estimated the damage caused by the slasher at hundreds of thousands of dollars, but other library officials said a more accurate figure is "several million."

"There's no way to put a price on some of these items because they are centuries old and many are irreplaceable," Johnson said.

The Harvard News Office yesterday issued a statement about what it called "the culmination of an intense four-year investigation."