Armed men dressed as mariachi musicians opened fire at the famous Plaza Garibaldi in Mexico City, killing four people and wounding nine others, including a foreigner, police said Saturday.
The five attackers opened fire with rifles and pistols shortly before 10:00 p.m. Friday (0300 GMT Saturday) while the downtown plaza was full of partiers enjoying the celebrations of the Independence Day weekend of September 16.
Investigators later found 60 empty bullet cartridges in the ground.
The shooters fled on board three motorcycles, the Mexico City prosecutor's office said.
Music and parties continued until after the city's public safety chief, Raymundo Collins, appeared at the crime scene, showed video footage on television.
"Four people have died, including a woman, and nine are injured, including a woman, as well as a foreign man," the prosecutor's office said Saturday.
Collins described the attack as a directed blow. No details were given about the identity of the foreign victim.
Initially, local police said three shooters had opened fire and three people had been killed and seven wounded.
The investigators have not given a reason for the shooting, but they did say that two of the murdered men, aged 36 and 46, had been convicted of robbery, while the older person had also been convicted on drug charges.
The shooting ended up emptying the plaza, one of the most popular attractions in Mexico City, and the restaurants and bars of the nearby streets.
Police patrol vehicles sat outside the premises on Saturday, usually bursting with customers seeking to pay mariachi musicians to perform.
Until recently, the capital of Mexico had been safe from violence related to organized crime that ravaged other parts of the country.
Most of the reprisals have taken place in the outskirts of the city or in areas where criminal gangs operate.
Plaza Garibaldi is located near the notorious neighborhood of Tepito, where a local gang that distributes drugs in the capital of 21 million inhabitants.
The police have linked that gang with larger cartels like the Nueva Generación Jalisco.
Mexico has been hit by a wave of violence since it deployed the army to fight the country's powerful drug cartels in 2006.
Since then, more than 200,000 people have been killed, including a record of 28,702 last year.
Another 37,000 people are reported missing.