QUINCY, Mass. -- Parents in Quincy are watching their children a little closer after threatening letters were delivered to their homes.

It happened several times in the last month, the latest incident on Easter Sunday, prompting an intensive police investigation.

Newscenter 5's Gail Huff reported that authorities are concerned enough that they're asking for the public's help finding the culprit. They've been finding threatening notes wrapped in women's underwear for several months, but are now going public in order to apprehend the person sending the packages.

The hand-written notes dropped at houses are composed on pages torn from the American Girl magazine, which is marketed to pre-teens.

"It threatened in a very graphic manner to sexually assault young girls. The graphic nature of the threats ... the person doesn't appear ... he has to know we're out there," Quincy Police Chief Robert Crowley said.

The first delivery was on Feb. 5 at a Mechanic Street rooming house. Among the 14 residents there is a level 3 sex offender.

The following February night a similar package was found on Endicott Street. On April 5, Franklin Street was targeted and on April 14, a package was found on Bradford Street. That note warned of an attack on Easter Sunday, and two days ago, on Easter, a package was found on Presidents Avenue.

"I mean, I live two doors down from this and it's startling. There's a lot of kids in the neighborhood," resident Mike Kilroy said.

The package found on Easter was wrapped in a holiday-themed envelope which has been sent to the state lab to see if evidence, such as fingerprints, can be collected from it.