More than 20 people were shot.
Gunfire erupted during the early hours outside a billiards hall in a row of businesses near Miami Gardens, northwest of the coastal city's downtown.
Three people climbed out of a white vehicle "with assault rifles and handguns and started firing indiscriminately into the crowd", police director Alfredo Ramirez III told reporters.
Florida remains marked by the 2016 shooting at the Pulse nightclub in Orlando, in which a gunman killed 49 people and wounded at least 68 others.
"These are cold-blooded killers who fired indiscriminately into a crowd", he said, stressing, "We will do justice".
The Florida mass shooting is one of a number that have taken place in the past few weeks in the United States.
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A search this week of the shooter's home - which was set ablaze shortly before the attack - turned up 12 guns, some 22,000 rounds of ammunition and suspected Molotov cocktails.
Miami-Dade Police Director Freddy Ramirez said Sunday morning that the shooting was a "targeted and cowardly act of gun violence". "This is targeted. This is definitely not random", he told reporters.
The events in Florida are just the latest example of deadly gun violence in the country.
The United States saw at least 200 mass shootings in the first 132 days of this year, according to a report by the Gun Violence Archive, a non-profit research group.
"This is a serious shooting ... there are many questions that remain", he said, including what type of weapons were used in this shooting.
In April President Joe Biden announced new actions to tackle gun violence.
The United States counted the deaths of more than 43,000 people with firearms past year, including suicides, according to the "Archives of Weapon Violence".