Tennessee Gov. Bill Haslam said it might take an act of Congress to help increase security at vulnerable military recruiting and support centers like the one that was hit in Thursday's Chattanooga shooting rampage.

Thursday's attack took the lives of five servicemen.

Haslam praised the FBI's efforts so far to figure out the motivation behind the attack and said his state is trying to figure out new ways to protect recruiting centers and other military facilities in the wake of deadly shootings.

The governor told Chuck Todd on "Meet the Press" that the state is reviewing whether it's "appropriate" for officers at these facilities to be armed "to a better degree than they were in the past."

But he said one of the challenges he and other governors are facing is that many of the military facilities in his state fall under federal control, which is out of state jurisdiction to ramp up security measures.

"We're concerned, obviously," he said. "We won't want to leave our folks out there as targets when we've had such a horrible event happen just three days ago."

Todd asked him if it would take an act of Congress to beef up security at federal military facilities located in states across the country.

"Ultimately, that might help clear things up because on federal grounds, we have limited authorities on what we can do," he said. "We're going to do everything we can. At the end of the day, it would be a lot better if we had clarity from the federal side."

The FBI is investigating the shootings as an act of domestic terrorism and are examining overseas travel by the alleged shooter, Mohammad Abdulazeez, as well as any ties or communications he may have had with extremist groups.

Abdulazeez, who was killed by police after the shootings, is accused of going on a shooting rampage at two military facilities in Chattanooga, Tenn., Thursday, killing four Marines and one sailor.

Abudulazeez's family issued a statement Saturday saying their son suffered from depression, which "found expression in this heinous act of violence."

The family offered sympathies, condolences and prayers to the family and friends of the victims and said there are "no words to describe our shock, horror and grief."

"The person who committed this horrible crime was not the son we knew and loved. For many years, our son suffered from depression," the family said. "It grieves us beyond belief to know that his pain found its expression in this heinous act of violence."

Michael Leiter, a former director of the National Counterterrorism Center during the Obama administration, told Todd there is a fine line between politically motivated terrorism and mental illness.

"Often those who have mental illness are most attracted to violent ideology," he said.

Unfortunately, what appears to be a lone-wolf act of domestic terrorism appears to be the new normal, he said, noting the country is experiencing a pattern of these attacks that began in 2009 in Ft. Hood, Texas, then in Arkansas with an attack on a military recruiting center, and then the attack in Garland, Texas at a cartoonist event, and another incident involving a machete attack on a New York City policeman.

"What we see are lone wolves who are motivated by [Islamic extremist terrorism], not driven, not directed" by specific individuals, he said. "But it is very difficult to control and stop, especially when you have soft targets like these in Chattanooga."