Harvard police arrested a man outside Grays Hall Wednesday morning for trespassing after he had been given a previous warning.

Andrew C. Warner, 21, a resident of Hopkinton, Mass., was arraigned later that day for the offence, according to police.

Early Wednesday morning, Harvard officer Joseph Crowley saw Warner "in possession of a green landscaping stake and was swinging it from side to side as pedestrians walk by," according to Harvard Police Chief Francis D. "Bud" Riley.

Crowley asked Warner to leave the property and to refrain from that kind of "hazardous" behavior, Riley said.

About 40 minutes later, a Harvard Yard guard, Mike O'Terrio, watched Warner trying to enter Grays Hall, according to Riley.

O'Terrio called Crowley, who immediately recognized Warner when he arrived on the scene, Riley said.

When Crowley reminded Warner that he had already given him a warning, Warner became belligerent and began screaming at the officer, Riley said.

As a result, Crowley arrested Warner for trespass and disorderly conduct, according to the chief.

Warner has no affiliation with the University, and Riley described him as a "homeless wanderer who frequents Harvard Square."

Police are also investigating an unusual stalking case involving a female summer school student living in Leverett House.

Riley said the female student, whom he declined to identify, first met the man involved in the case two weeks ago in front of Eliot House. There he identified himself as an MIT student.

Although the two have not seen each other since their initial encounter, the man has made a series of harassing phone calls, according to the chief.

"Now it's gotten to the point where she doesn't want to deal with it anymore," Riley said.

Police have moved the summer student to a different dorm room and are seeking the identity of the stalker, Riley said.

The student has not had contact with the stalker since she moved, according to the chief.

Riley described the man as Asian, about six feet tall and in his twenties. Riley said this is one of the first stalking cases he has had during his term as chief, which began around the New Year.

"Most of the incidents even related to that are people who are unknown to each other--women who have become aware because of all the safety awareness [campaigns]," Riley said. "But we haven't had any that we've actually prosecuted.