10 days ago, at twilight, four teenagers approached someone affiliated with Harvard near Peabody Terrace, pushed him to the ground and stole his wallet. The police response was swift. Units from the Cambridge Police Department (CPD) and the Harvard University Police Department (HUPD) canvassed the area, but couldn't find the robbers.

The next day, HUPD issued its thirteenth community advisory, warning the University of yet another threat.

The advisories are becoming nearly commonplace this fall, as violent crime against Harvard affiliates has risen.

The trend has police searching for answers, and has concerned students and college administrators.

A significant detail of the trend, though, is its randomness.

The pattern is that there is no pattern: four undergraduates assaulted by alleged skinheads, another two assaulted by persons unknown, two affiliates indecently assaulted, one sexually assaulted, four street robberies on Harvard's campus, and a serious unprovoked assault on a runner on the bike path near the River.

Bike theft is up. Larcenies from motor vehicles are up.

While last year, HUPD's first community advisory was issued in mid-October to warn about the Yard Burglar, HUPD has already issued 13 this fall.