SAN JUAN, P.R. — An afternoon of extraordinary protests demanding the immediate resignation of Gov. Ricardo A. Rosselló of Puerto Rico turned chaotic late on Monday when police in riot gear launched tear gas and pepper spray into a crowd of thousands of demonstrators.

The volleys of gas just after 8:30 p.m. dispersed much of the gathering that had swelled outside of the governor’s mansion, La Fortaleza. But some protesters defied the authorities, sitting in a row in front of the police wall, raising their arms and holding hands.

“¡Somos más y no tenemos miedo!” they yelled. There are more of us, and we are not afraid.

[Update: Puerto Rico governor insists he will not resign.]

One man, his face covered in a black bandanna, urged the officers to move, reminding them that they, too, are Puerto Ricans. Another man, his face bare, stood silently, shaking his head.