Masked gunmen have killed at least 19 people and injured seven more in a series of shootings on the outskirts of Brazil’s largest city of Sao Paulo, authorities say.

“This is very serious and merits a special investigation,” said Secretary of Public Security for Sao Paulo State Alexandre de Moraes in a Friday statement. “We don’t rule out any possibility.”

According to de Moraes, the shootings were the “largest killing of the year” that occurred Thursday night local time. He further added that a total of 15 individuals were killed in the city of Osasco, three in Barueri and one in Itapevi, all of which lie within Sao Paulo’s metropolitan area  (…)