WASHINGTON - Now President Joe Biden gets to question the mental fitness of former President Donald Trump.

The 81-year-old Biden, who is still being flayed by Trump over age and stamina, is getting into the act over the Republican presidential nominee's music-and-dance-a-thon at a suspended campaign town hall on Monday, saying his 78-year-old longtime political foe has "snapped."

"He's become unhinged," Biden said during a campaign event for Vice President Kamala Harris on Tuesday.

"Look at his rallies," Biden said. "Last night, his rally stopped taking questions because someone got hurt. And guess what? He stood on the stage for 30 minutes and danced ... I'm serious! ... What's wrong with this guy?"

Trump, speaking on Truth Social, said "we started playing music" and "just kept it going" when the event was interrupted by a pair of medical emergencies. "So different, but it ended up being a GREAT EVENING!" he said.

Still, the mini-concert - at times, Trump stood perfectly still; at other times, he bobbed to the beat in a robotic-like manner - provoked more questions about his mental state, including a barb from Harris.

"Hope he's okay," Harris said on the social media platform X.

Earlier this year, Trump made Biden's age and mental health the key issue of the campaign. Biden's halting performance in a June 27 debate sparked Democrats to go public with concerns over the incumbent president's ability to carry out a general election campaign against Trump and to serve another four years had he won. Ultimately, Biden withdrew from the race and endorsed his vice president as a replacement.

While Trump still mocks Biden, the Democratic president seemed to relish the chance to get back at the GOP candidate after Monday's town hall.

"Trump hasn't changed," Biden said Tuesday. "I would argue he's gotten worse."

Karoline Leavitt, the Republican nominee's national press secretary, responded to the president's comments with her own jab: “Nobody cares what Joe Biden has to say anymore," she said. "That’s why his own party kicked him off the ballot.”

(This story has been updated with new information.)