Rep. John Dingell, dean of the House, wants to investigate whether gun control laws targeting mentally unstable individuals are working in the wake of the Tucson shootings.

“If what we understand is so that we have here is somebody who is mentally disturbed is having an easy time to get a gun and whose warnings of his behavior are not finding its way into the National Instant Check System, we’re having perhaps a serious problem that perhaps needs to be addressed,” the Michigan Democrat said Wednesday.

Dingell said he has contacted the Government Accountability Office to see if the law is being properly enforced.

Dingell worked alongside then-Rep. Rick Boucher (D-Va.) and Rep. Carolyn McCarthy (D-N.Y.) following the Virginia Tech shootings in 2007 to make a bill increasing funding for the National Instant Criminal Background Check System. The bill, which later became law, set aside $250 million a year for three years to help states to automate and report information to NICS.