The Harvard University Police Department (HUPD) now has "solid leads" in the "unprecedented" crime wave in the Yard dorms, HUPD spokesperson Peggy A. McNamara said yesterday.

McNamara said detectives now believe that the crimes in Matthews and Thayer Halls are the work of a single perpetrator.

"He's like a shark and he's come into a feeding frenzy," she said.

McNamara said HUPD has refined its description of the suspect and is seeking a 5-foot 10-inch light-skinned black male between 18 and 22 years old. Past descriptions had only referred to the Thayer burglary and omitted the suspect's age.

HUPD also said for the first time yesterday that the credit cards taken over the past three weeks have been used since they were stolen, but did not release the locations of their use.

Matthews Hall was first burglarized on Oct. 3, and now a total of seven Matthews suites have been robbed. On Oct. 12 a student entered his Thayer Hall suite while a robbery was in progress, and police suspect the same man committed all the crimes.

HUPD believes that a larceny last week in Weld Hall is not related to the other crimes.

According to McNamara, HUPD has stepped up Yard patrols and added undercover officers in the wake of the incident.

HUPD officers are worried that the robber may be getting more "brazen"--striking during daylight for the first time this weekend.

McNamara urged students to be on the lookout for the perpetrator, who she said "seems to fit in" with students. She said they should approach unfamiliar visitors and ask if they need help. Students should call HUPD if they are still suspicious, she said.

McNamara also urged students not to challenge the perpetrator on their own. She said that police do not want to see a repeat of last week's confrontation in Thayer, during which students wrestled with a robber and then chased him down the hall.

"Call us, let us do our job," McNamara said. "We'd rather have the robber get away than have a student injured."

Dean of Freshmen Elizabeth Studley Nathans said her office is "extremely concerned" about the incidents and has received calls from concerned parents. She has referred some of them to HUPD for more information about dorm security.

Gervasio A. Lamas '74--whose daughter was robbed in the third Matthews wave--said he was taken aback by the crime and has an appointment to speak with Nathans this morning.

"This stranger entered a room with two sleeping young women, and my daughter taking a shower who could have come back at any moment," he said. "It might have been a rape or worse. I was terrified."

Lamas said Harvard should install locks that shut automatically in all dorms and step up patrols in the Yard.

"There are certain realities that I take for granted are part of the tuition money that I pay," he said. "One of them is that the men and women who are part of the University have appropriate security."

HUPD officers expressed frustration yesterday that students are still not locking their doors.

"If you don't give him the opportunity, he can't commit the crime," McNamara said.

Matthews resident Crystal E. Carpino '03 is one student who says she has taken steps to tighten security in her room, including hanging a "Lock the door!" sign on the door.

But Carpino--who said she is lucky to have escaped the recent robberies--said she is not sure others are following her example. She visited a friend the other night and found the room unoccupied, but unlocked.

"Some people learn and some don't," she said.

But Lamas said police should come up with other solutions.

"It's easy to say 'you guys should lock your door and shut up,'" Lamas said. "There's an element of blaming the victim in that. Freshmen will be freshmen."