By Esme Murphy

MINNEAPOLIS (WCCO) — The FBI’s open-then-closed investigation into Omar Mateen’s history raises the question: How many other home-grown terrorists are being investigated, and how many are still a threat that may have dropped off the radar?

Mateen had been investigated by the FBI for 10 months starting in 2013 before the FBI had closed the case.

The question is especially of concern here in Minnesota. In the past decade dozens of young Minnesota men have left or tried to leave to join the terror groups al-Shabab and more recently ISIS.

In a visit to Minnesota just six days ago, FBI Director James Comey said the FBI was investigating close to 1,000 people for terror ties.

“The Bureau has close to 1,000 open cases in all 50 states focused on people who are at some stage between consuming the poison from the group we call ISIL to acting on that poison either by traveling or by moving towards violence here in the United States,” Comey said.

By “consuming the poison,” the FBI director was referring to watching ISIS propaganda videos. Testimony in a four week terror trial in Minneapolis that ended earlier this month revealed the FBI’s intensive surveillance of social media for ISIS supporters and for anyone who is contacting terror groups.

But voicing support for a terror group or contacting a terrorist as Mateen apparently did is not enough to get you arrested. Dan Scott was the chief public defender in Minnesota’s federal court system.

“There are a lot of people who talk and talk is cheap. It’s whether they are going to act,” Scott said.

In the Minnesota terror trial, three young men were convicted for their actions — all found guilty of trying to leave the country to join ISIS. All face life in prison.

Last week Comey said publicity surrounding the Minnesota case and others may be behind a drop in U.S. citizens trying to leave the country to join ISIS. But the drop also left him fearing the very route Mateen took.

“Which is a more disturbing possibility is that people are staying home because they know we might catch them if they travel and looking to do things on behalf of the Islamic State at home,” he said.

The FBI says while Mateen was on a terror watch list he was later taken off the list because the FBI believed his link to terror groups was minimal. The nearly 1,000 cases the FBI director referenced last week are open cases. We don’t know how many Mateens there are — people who were investigated, are no longer on the FBI’s radar and could still pose a threat.

Esme Murphy