Officer Joseph Mensah of the Wauwatosa, WI, police was physically assaulted outside his home Saturday night and a single shotgun round was fired into the home after a group of 50 to 60 people gathered there to protest. Mensah has fatally shot three people over five years. Two of the shootings have been legally justified. The third happened earlier this year and is under investigation.

On Saturday, protesters began to vandalize Mensah's home around 8:05 p.m., according to a news release from Wauwatosa police. Mensah "attempted to establish a dialog but was physically assaulted," the release said.

As Mensah went inside, "armed protesters approached the rear door and a single shotgun round was discharged by a member of the group into Officer Mensah’s backdoor," the release continues.

Several other police departments were called to help disperse the crowd, the Journal Sentinel reports.

In a Facebook post, Mensah said he was home with his girlfriend and that the shotgun shell missed hitting him by inches.

Mensah's Feb. 2 fatal shooting of Alvin Cole is still under investigation. The shootings of Antonio Gonzales and Jay Anderson Jr. were deemed justified self-defense by the Milwaukee County District Attorney's Office.

Former Wisconsin Gov. Scott Walker on Sunday tweeted that the mob attack on Mensah is "domestic terrorism" and officials must take action.

Wauwatosa Mayor Dennis McBride said he would be meeting with the police chief and other city officials Monday morning to ensure Mensah is “fully protected and that criminal behavior of this kind will not happen again.