DETROIT – As the country mourns, we've learned more about the dark digital world that's become a breeding ground for domestic terrorism.
"I think this hate-driven speech is more pervasive. It's, to a certain extent, more accepted today than it was when I was in the FBI," said Andy Arena, with the Detroit Crime Commission. "I think that's why you've seen this uptick in domestic terrorism and domestic violence. These people feel emboldened. They feel like they're not being challenged, that they can get this out there and that people accept what they say."
Arena spent seven years as the special agent in charge of Detroit's FBI office. He's now the executive director of the Detroit Crime Commission. He spoke with Local 4 Defenders about websites and online bulletin boards where messages of violent racism and hate can spread.
Investigators said Patrick Crusius, the man believed to be responsible for the deadly El Paso shooting, posted his plans on 8chan just before the attack. Additionally, two other mass shootings this year -- the mosque attack in New Zealand and the synagogue shooting in California -- have been announced in advance on the website.
In July, the director of the FBI said the agency has made about 100 arrests related to domestic terrorism since October.
"A majority of the domestic terrorism cases that we've investigated are motivated by some version of what you might call white supremacist violence," said FBI director Christopher Wray.
Arena said there are challenges for investigators when it comes to what's said online.
"From the FBI perspective, it's difficult because much of this is protected free speech. So the FBI cannot go on fishing expeditions and look for this," Arena said. "They have to have reasonable suspicion that this is hateful and it will incite someone to do something."
Now the FBI is concerned that more domestic violent extremists could be inspired by the recent attacks in El Paso and Dayton. The agency wants the public to report suspicious activity they see in person or online.
"In a large majority of the attacks, over 85% of them over the years, there was at least one bystander. A bystander is somebody that has access to information that would've been deemed suspicious activity or could've potentially alerted law enforcement," said FBI Supervisory Special Agent Devin Kowalski. "But only half of those instances did that bystander report the information to law enforcement."
Kowalski said it's the people closest to a potential threat that they need to hear from.
"Whether it be at school or with their employer or with their family members, that's where they'll show signs of, we'll say, deterioration," Kowalskis said. "So we rely on those individuals that are in that person's physical network, as limited as that may be, because these are introverted individuals that rely on a virtual network of like-minded individuals."
While investigators believe the motivation for the El Paso shooting was hate, authorities in Dayton are still trying to determine that shooter's motivation. The Dayton police chief said the suspect had a history of obsession with violent ideas and had expressed the desire to commit a mass shooting.
You can report threats, crime and suspected terrorism at the FBI's official website here.