Norfolk Police Lt. William K. Kelly lost his job after a hack revealed the names of those who gave money to help with the 18-year-old's legal costs
Rittenhouse is accused of killing two protesters and wounding a third during a demonstration against police brutality in Wisconsin last August 25
Kelly, who was second in command in the Norfolk Police Department's internal affairs division, is said to have written: 'God bless. Thank you for your courage'
He added: 'Every rank and file police officer supports you. Don't be discouraged by actions of the political class of law enforcement leadership'
City Manager Chip Filer said: 'His egregious comments erode the trust between the Norfolk Police Department and those they are sworn to serve'
Kelly has not commented; the 19-year veteran can appeal the decision
Conservatives have rallied around Rittenhouse, painting him as a symbol for gun rights; they generated money to help with his $2million bail in November
Rittenhouse has pleaded not guilty and argued he fired in self-defense