The most common threats are made by direct telephone calls to the Police Department. However, some threatening calls are made to third parties such as television studios and newspaper offices.
There are two reasons for a caller to report that a bomb is to go off at a particular location:
- The caller knows that an explosive or incendiary device has been or will be placed in the building and wants to minimize personal injury. The caller may be the person who planted the device, or just someone who is aware of such information.
- The caller wants to create an atmosphere that spreads panic and disrupts normal business activity. This could be the ultimate goal of the caller.
- Letters that are unusually bulky or weighty.
- Parcels or envelopes with chemical or oily stains.
- Parcels or envelopes without a return address.
- Parcels or envelopes with foreign postmarks.
- Parcels or envelopes that simply do not look or feel ordinary.