Fifty-five-year old Christina Bond who worked for the Republican Party was airlifted to hospital shortly after but died shortly after.
The incident happened on New Year's Day in Michigan but police have only just released the details. It comes amidst a long running debate that's been ongoing over the country's gun ownership laws and whether they should be tightened.
In a Facebook post, her son Nick said: "Tonight God lost his most powerful soldier on earth - my mother. How cliché are the words 'that can't happen to me'. In this moment, I am that man - and it happened.
"My mother was the strongest person I have ever known. It's in her, that I've become who I am. She gives me strength to stand up for what I believe. She gives me courage to fight for the truths that I hold dear."