SAN JUAN, P.R. — The man streaming on Facebook Live looked straight into his cellphone camera and promised that the footage to come would be outrageous. “Share what you’re about to see,” he urged his viewers.

Moments later, he walked into a huge warehouse and revealed his discovery: cases of bottled water still encased in plastic. Pallets of new diapers, baby formula and wipes. Boxes of wrapped tarpaulins, portable stoves and propane gas.

Unused emergency aid sat gathering dust in a government property in the city of Ponce, in southern Puerto Rico, as thousands of people prepared to spend their third week sleeping outside to stay safe as a swarm of earthquakes continued to assail the island. The water appeared to be expired, the man on the video said. But there were no signs of emergency workers or any effort to distribute the disaster supplies.

The video, streamed on Saturday by Lorenzo Delgado Torres, who calls himself “El León Fiscalizador,” or the lion of accountability, immediately exploded on social media. Infuriated Puerto Ricans showed up at the 43,000-square-foot warehouse to demand an explanation, jeer at government officials and take some of the supplies. Someone called police officers, who closed off the street.