As candidates exchanged pleasantries and handshakes on stage, Elizabeth Warren approached Bernie Sanders, who stretched out his hand for her to shake. But Warren either didn’t see — or rebuffed him, and a tense exchange followed.

Warren gestured with her right hand, then clasped both hands together while addressing a seemingly surprised Sanders.

Warren kept speaking to Sanders, who nodded, then put his hands up as if to stop her. Both spoke, as Tom Steyer approached the pair. Then Sanders seemed to offer a few sentences before both turned their backs — Sanders a split second before Warren — and walked away.

Neither campaign immediately spoke about what was said. Asked afterward, Steyer said he had no knowledge of the apparent skirmish.