An unidentified homeless man threatened a Widener Library attendant, smashed a display case and stole a gold-plated ceremonial key on Tuesday, according to police officials.

The man, who used an ink quill to intimidate the room monitor, ran from the second-floor Widener Room to the library's basement and "disappeared," according to Harvard University Police Chief Paul E. Johnson.

"I heard a loud clanging downstairs at around 12:30 p.m.," said security guard Maure H. Brennan. "Then I heard a woman screaming. I called security and I called police."

Earlier in the day, police officers had escorted the man out of the library after he locked himself in a room outside the Widener Room. The man offered no resistance when the police unlocked the door and removed him, Johnson said.

The earlier incident likely prompted the theft, Johnson said.

"He was angry at being ejected in the first place," Johnson said. "He was probably just acting on his anger."

Johnson said the police know that the man frequents a homeless shelter in Bostonand have issued a warrant for his arrest.

Harvard police recovered the key on the groundbetween 5 and 7 Linden St. yesterday.

Johnson said students should not be concernedabout their safety at Widener despite Tuesday'saffair.

"I don't think this incident is any indicationof worrisome trends in the operation of WidenerLibrary," Johnson said. "This was an abberationdue in part to the growing community of homelessand disturbed people."

But Widener officials said the library systemhas plans to beef up security. "Widener is awide-open building and it shouldn't be," saidLarsen Librarian of Harvard College Richard DeGennaro. "We should have much tighter security."

A sign outside the front door at Widenerrestricts visitors to "members of HarvardUniversity and Radcliffe College Alumni and otherswho have been granted library privileges."

But Widener security officer David Muir saidcheckers are not required to examine theidentification cards of people entering thebuilding.

"The library has been traditionally open tomembers of the public to come by and take a lookat exhibits," Muir said.

"That sign is in effect, but we do not enforceit," De Gennaro said. "We hope people will observethe sign, but there is no system for enforcingit."

Widener currently issues library cards topatrons who are not Harvard students. But becausethe cards have no pictures, De Gennaro said,checking them would be useless.

According to De Gennaro, the University isconsidering implementing a plan next year thatwould issue picture IDs to all authorizedindividuals and would install a book-theft alarm