Transcript for Police Chiefs Around the World Try to Combat Violent Extremism and Gunmen
In the past year low rules and active shooters have been particularly deadly. Challenging law enforcement agencies around the world this is an ABC news. We're coming on the air right now because we're learning about a series of shooting incidents in the capital of Canada aren't over 22 2014. Ottawa Canada a soldier or on duty at the war memorial is shot in cold blood the killer entered Harvard. Engages in a shootout with security off. The gunman and Islamic radical with mental health issues January 7 2015. Paris France. Two Brothers forced their way into the offices of weekly newspaper Charlie have dealt. And massacre eleven people tonight across France the terror alert now its highest level five more are murdered over the next few days he related attacks. Before the terrorist or cornered and killed. The gunman self proclaimed Islamic radicals June seventeens 2015. Charleston, South Carolina. A young man walks into a Bible study at a historically black church. And guns down nine in this an African Americans are enforcement officials were greatly concerned about what he might do next was he saw motivated did he act alone the gunman soon captured. A young men seething with hatred stoked by the unit it. Hoping to spark a race war. And only about a month later July 16 2015. Chattanooga Tennessee a 24 year old goes on a murderous Rampage at two military installations. This is the nightmare scenario officials had been concerned about the gunman a lone wolf. Allegedly radicalized on the Internet. All active shooter scenarios. All mass casualty situations. And but the people pulling the trigger. Had different motivations this summer in the US the rising threat of homegrown terror was front and center. The temple for the FBI and counterterrorism officials never more intense. The concern in recent weeks particularly around the fourth of July. Have been in people inspired by Tyson's might attempt an attack of some sort FBI director James Komi warned. Of an unprecedented social media campaign by our seats they're pushing this through Twitter so there is a device almost the devil on their shoulder all day long saying. Kill kill kill kill. The FBI says this North Carolina teenager. Influenced by a crisis allegedly planned to kill his parents and gunned down more than 1000 people. You know any of this is going off now. And a college student from queens New York radicalized online. Charged by the Justice Department allegedly planning to bomb the George Washington Bridge last summer. These just two of more than forty cases against alleged ices recruits and the first six months of 2015. Before the advent of this new technology. And the growth of social media how would you reach into the basements and bedrooms of American homes. ABC news took a closer look at the crisis so soon media campaign. Aimed primarily at young people. We found is not just brutal bee headings and radical rants. Look at this Twitter posting. It shows ice is fighters handing out candy and ice cream to children. This is Madison avenue meets documentary film making needs news channel with PR sensibilities and a marketing value. But while the threat of homegrown terrorism is always in the forefront. Other active shooter incidents are painful reminders. The deadly threats can come in many forms we've seen two journalist shot and killed online television and earlier this month in Oregon. A gunman turned the classroom into a bloody slaughter house no matter what this bars he's vicious attacks. The ever present challenge for law enforcement around the world. Is to be prepared for all of it.
This transcript has been automatically generated and may not be 100% accurate.