ST. LOUIS -- A man has been ordered to spend a year and a half in federal prison for a cyberattack that disabled a St. Louis-area police union's website during unrest related to the fatal police shooting of Michael Brown.

Justin Payne, 33, was sentenced Monday in St. Louis. That's where he pleaded guilty in September to a felony count of possessing an unregistered firearm and a misdemeanor count of damaging a protected computer.

Investigators said the unregistered firearm was a crude incendiary device commonly called a Molotov cocktail.

Payne was accused of using Twitter accounts to unleash the December 2014 cyberattack that overwhelmed the St. Louis County Police Association website. Authorities say his actions were part of the "Operation Ferguson" effort supporting protesters of last year's shooting death of Brown in Ferguson.