Defining Terrorism

We are all shocked by what happened in San Bernardino County with the mass killings and shootings. We all wondered what terrorists were involved? What was their motive? Why attack this particular office building?

I've been listening to various news reports about the definition of "terrorism" and all I can say is anytime any one person or two people or more walk into a building or show up in a public place and start killing -- it's terrorism. They don't have to be waving a flag or have a political agenda. They are causing terror.