One of the nation's leading gun-control groups is filing a lawsuit against the makers and sellers of "bump stocks," the devices used by the gunman in what is now the deadliest mass shooting in modern U.S. history.

The Brady Campaign to Prevent Gun Violence says it's filing the lawsuit on behalf of victims to pay for counseling and other treatments. It's also asking the court to award punitive damages against the leading manufacturer of bump stocks.

The devices, originally intended to help people with disabilities, replace the stock and pistol grip of a semi-automatic rifle and allow the weapon to fire continuously, mimicking a fully automatic firearm. Bump stocks were found among the weapons used by Stephen Paddock as he shot from a Las Vegas casino high-rise Oct. 1, killing 58 people at a concert and wounding hundreds.