Gangs stormed the neighborhood of Haiti’s police chief, Frantz Elbé, in March, broke into his house, set it afire and killed his dog.

Mr. Elbé and his family were not home at the time, and he did not want to discuss what happened in any detail. But the attack, which was captured on video, sent a chilling message through police ranks and to residents of the country’s embattled capital, Port-au-Prince.

“It symbolized that no one was safe,” said Reginald Delva, a Haitian security consultant and former Haitian government minister.

The torching of the police chief’s house deepened fears among Haitians that their country was on the brink of collapse in the face of an onslaught by a coalition of armed gangs that had seized control of…