Recent acts of domestic mass violence, including the killings at a movie theater in Aurora, CO, last month, have involved extensive planning, according to police. 

With long-term planning often comes suspicious activity that might be detected by alert citizens.

Montgomery County police have issued a video called The Seven Signs of Terrorism that gives tips on how residents can help authorities in their effort to thwart plans for terror attacks.

Police Chief Thomas Manger talks about patterns of behavior for which to be on the lookout in your community, in the accompanying video.