His resignation, effective Aug. 2, came late Wednesday night on a recorded video published on Facebook. In the message, he touted what he considered accomplishments of his tenure, saying he fought corruption and made strides for different communities.
"My only North Star has been the well-being of my island," he said.
Crowds in the streets, which for almost two weeks had been calling for the governor to step down, immediately erupted in joyous chants, cheering "Puerto Rico! Puerto Rico!"
"Ricky, te botamos!" ("Ricky, we threw you out!") the jubilant crowd chanted after the governor's announcement.
"After the birth of my son, this is the happiest day of my life," acclaimed Puerto Rican reggaeton star René Pérez Joglar, also known as Residente, said. He was among the artists who had galvanized the island in rallies that were unprecedented in their scope.
In the report that was leaked to the press, the attorneys found Rosselló committed four serious offenses and one misdemeanor, including illicitly using public resources and services for partisan purposes, as well as allowing government officials and contractors to misuse public funds and time for nongovernment work.
Rosselló's announcement came after a day of mounting frustration as reporters gathered in front of the governor's mansion for the anticipated announcement and thousands of people gathered nearby in Old San Juan chanting, "Ricky, Renuncia!" ("Ricky, Resign!")
Reports of Rosselló's planned resignation had broken Tuesday, a few hours after NBC News and Telemundo, both owned by NBC Universal, reported that the island's Justice Department had issued search warrants to confiscate the cellphones of several people who took part in the private chats.
Hundreds of thousands of Puerto Ricans have been protesting for 12 consecutive days, demanding Rosselló's ouster. Protests continued to grow on the island after Rosselló announced Sunday that he wouldn't run for re-election and that he would step down from the leadership of the pro-statehood New Progressive Party.
On Monday, more than half a million people paralyzed metropolitan San Juan in protest, marching across one of the main highways despite heavy rain in a "March of the People" that ended late in the night as police fired tear gas canisters.
The leaked chats on the messaging app Telegram rocked the public for their profane, misogynistic and homophobic comments against public officials, celebrities and ordinary islanders, as well as their cynicism on topics that included the deaths following Hurricane Maria in 2017. The chats also revealed the administration's efforts to smear and bring down political opponents.
The leaked messages resulted in the opening of local and federal probes, which came on top of recent arrests of former officials and government contractors on charges that include fraud involving federal funding. Investigators are looking into possible wrongdoing such as corruption and conflicts of interest.
By law, the island's secretary of state would succeed Rosselló, but no one has been confirmed for that position since Luis G. Rivera Marín, who was part of the chat scandal, submitted his resignation July 13.
Justice Secretary Wanda Vázquez is next in line.
"Once the resignation is official, if necessary, I will assume the historic mandate that the Constitution of Puerto Rico commends," she said in a statement.
Vázquez, who was appointed in 2017, is seen as loyal to Rosselló and the hashtag #WandaRenuncia (or "Wanda, resign") started trending on Twitter immediately after Rosselló's address ended.
Vázquez initially described the leaked chats as "incorrect" but not illegal. She later announced that she would recuse herself from any investigation because she was mentioned in the chats.
Nicole Acevedo reported from New York, Alex Johnson from Los Angeles and Gabe Gutierrez from Puerto Rico.