Gunmen have killed at least 19 people on the outskirts of Brazil’s largest city, Sao Paulo, in a series of overnight attacks.
Witnesses in several locations said masked gunmen pulled up in a car before opening fire.
In many cases they checked the victims’ names before shooting, or asked if they had criminal records.
The authorities in Sao Paulo are investigating the possibility that they were targeted killings.
Such attacks carried out either by criminal gangs or rogue police officers are not uncommon in Sao Paulo, says the BBC’s Wyre Davies.
But police say the number of victims is much higher than in previous incidents.
“I’ve never seen so many people killed overnight in Sao Paulo,” a forensic expert told Folha de Sao Paulo newspaper.
The attacks happened in the municipal areas of Osasco, Barueri and Itapevi.
At least seven other people were injured in the shootings.
“This is very serious and merits a special investigation,” said Sao Paulo state Security Secretary Alexandre de Moraes.
“We don’t rule out any possibility.”
A task force of 50 police officers has been set up to investigate the attacks.
In May, a policeman and a former policeman were arrested in connection with the murder of eight men at a football fan club in Sao Paulo.
The former policeman was accused of ordering the attack against supporters of the Corinthians football club.
They were preparing banners ahead of a match in April when gunmen burst in.