Donald Trump wasn’t happy to hear that Bruce Springsteen hasn’t backed down from calling him an “unfit president” as he performs in Europe, so he went on another rant on social media overnight Sunday, demanding a “major” investigation be launched against the rock ‘n’ roll legend for singing at a Kamala Harris rally in October.

“Things are happening right now that are altering the very nature of our country’s democracy, and they’re too important to ignore.”

The rock icon is showing no signs of backing down, delivering a fiery performance from a stage in this city Saturday that reflected the stark political divide in America.