Cambridge Police report  the communications about an alleged rifleman in body armor at MIT  on Saturday came via an "an internet relay" usually used to let people with hearing or speech impairments communicate:
The relay service used in this instance was a Sprint relay service, and a Sprint employee notified the police department of the conversation with the reporting party.
During this conversation, a possible suspect was mentioned and police immediately identified and interviewed him. After questioning, police determined that this individual had no knowledge of the incident and do not believe he was involved in making this false report at this time.
Police add they are continuing to work with police at MIT as well as the FBI and Secret Service to collar the person who sent the messages that led police to shut down MIT buildings and Massachusetts Avenue Saturday morning. If found, the person will face criminal charges, police say.
These relay services have become a common channel for swatters  to send in fake reports of dangerous situations, in the hopes of summoning the local SWAT team to somebody's house. Just last week, in fact, a SWAT team descended on Clint Eastwood's California home  after a relay message to 911 reported "multiple males armed with assault weapons inside the actor's house and people had been shot."
Last summer, a Murfreesboro, TN family found themselves confronted by gun-toting SWAT officers  after somebody swatted them.
In 2008, a Worcester teen was convicted  of swatting people across the country as a way of settling grudges with fellow gamers.