He had left the door to his bedroom open to “create a cross breeze” during a small party in his room. Although he knew most of the guests at the party, he wrote off a few unfamiliar faces as prefrosh.

When he went into his room after the party, his laptop was gone.

In her email, Chapman cautioned students to monitor who follows them into the House when they flash their IDs to enter the locked building.

But students acknowledged that her advice can be uncomfortable to follow.

“It’s sort of hard when [you think you’re] going to seem paranoid,” Kim said about questioning piggybackers before allowing them in. “It’s usually a good idea to be better safe than sorry.”

—Staff writer Amy Q. Friedman can be reached at afriedman@college.harvard.edu.

This article has been revised to reflect the following correction:

CORRECTION: April 24

An earlier version of this article stated that Melanie J. Comeau ’13 wrote in an email to Quincy House residents that she had seen four young men whom she believed to be responsible for recent thefts of laptops from Quincy playing pool and sitting in the dining hall in the House. In fact, although Comeau wrote in her email, “I am quite positive I know who is responsible for at least two thefts,” she wrote that she had spoken to many people who had seen the four young men, not that she had seen them herself.