Six women and five men enjoying a quiet Sunday afternoon at a bar in the Brazilian city of Belem were killed by a gang of seven gunmen who came on a motorcycle and in three cars.
One of the clients at the bar who suffered serious gunshot injuries is being treated at a city hospital.
Local authorities called the incident a massacre but declined to give details.
The gunmen sped away after committing the crime.
The incident comes two months after the National Guard troops were sent to Belem to secure the city and two days after a report said the number of killings in Brazil fell 24% to 10,324 in the first quarter.
Last year, 51,589 people were killed in incidents of violence across the country. In 2017, police reported 64,000 cases of homicides. Most cases of violence involved criminal gangs.
Some of the crime-infested Brazilian cities are Rio de Janeiro, Fortaleza, Belem, Feira de Santana, Maceio, Teresina, Joao Pessoa, Recife, Manaus, Macapa, Salvador and Aracaju.
Early this year, gang attacks brought life to a standstill in Fortaleza.
Onlookers often get caught in crossfire in Rio where not a day passes without gang wars and encounters between police and criminals.
President Jair Bolsonaro’s recent gun reforms allow people to carry firearm to defend themselves against gun-toting criminals.