The event was broadcast by Fox News.
After completing his speech on the topic of building and rebuilding infrastructure in the United States, Biden turned around in the opposite direction from leaving the stage.
The American president gesticulated for several seconds, said something aloud, after which he turned around and walked to the exit from the stage.
Earlier, Biden made a mistake during the speech, saying that his son Bo died during the fighting in Iraq, although he died of cancer in 2015.
At the end of September, during a conference in Washington, Biden tried to find a member of the US House of Representatives, Jackie Valorsky, who died in August in a car accident.