King Carter was playing Saturday afternoon in Blue Lake Village when "two unknown black males exited a dark four-door sedan and began shooting, striking Carter. The gunmen and driver then fled the complex in the vehicle in an unknown direction," the Miami-Dade Police Department said in a statement.
Police say they are looking for three black men. The make and model of their car is unknown.
"Clearly, he's not the target. He happened to be an innocent bystander, outside playing, doing what kids do," Miami-Dade police Director Juan Perez told CNN affiliate WPLG
. "I'm angry. Our officers are angry. The community behind me's angry, so hopefully they're angry enough that they could provide some information that will lead to the arrests of the individuals."
King was rushed to Jackson Memorial Hospital, where he later died. Family members at the hospital began wailing upon learning the youngster had died, WPLG reported.
The boy's father, Santonio Carter, posted a Facebook video
from outside the hospital, in which he asked people to pray for him.
"Just lost my son, 6-year-old King Carter. Y'all seen me with him everyday, man," he said before decrying the gun violence and "n**gas doing dumb s**t" in his community.
The grieving father, whose teen brother was killed in an accidental shooting in 2003, later directed his words toward his son's killer, telling WPLG, "It's so easy to get a gun. It's cowards. ... Where the real men at? They're missing their daddies, and my son had a daddy and his daddy's standing here before y'all, fed up."
Family members described the first-grader at Van E. Blanton Elementary School as a joyful boy who loved sports, especially football, as well as cartoons, especially "Teenage Mutant Ninja Turtles."
The boy's aunt, Tawana Akins, asked community members to attend a 2 p.m. Sunday vigil near the site of the shooting. She asked attendees to bring white candles and white balloons, and to wear "Ninja Turtles" attire, according to a Facebook post.
The area's problems cooperating with police -- particularly in the Liberty City neighborhood about a mile and a half south of where King was shot -- have been well-documented
, and Akins joined Perez and Miami-Dade County Mayor Carlos Gimenez in urging witnesses to reach out to authorities.
"If you know what happened, please say something," she said during a news conference. "A 6-year-old -- just think of your life at 6. It could easily be your family next."
The local Crime Stoppers chapter has put up $5,000 and Gimenez's office announced a $20,000 reward for information leading to the shooters' arrests.
"We need (the community) to tell us what's happening," Gimenez told WPLG. "Then we can get to the bottom of it quicker, put less lives at risk and put the perpetrators behind bars."
Akins expressed confidence that there are witnesses, stating on Facebook, "Too many people were out to not see anything. ... You helped me lock up the other coward who killed my other nephew last year. Do it for us now in Jesus' name."
Perez seemed equally confident that his officers would find those responsible.
"Right now, we're hunting for you. If you're involved, you may as well turn yourself in because I don't believe the community's going to stand idle on this. I think the community's going to stand tall and will hand these individuals up to us," he said.
According to a tally from WPLG, at least 67 people age 18 or younger have been killed by gunshots in Miami-Dade County since 2013.
In December, a boy not much older than King -- 7-year-old Amiere Castro -- was inside his home when he was struck by a bullet from a drive-by shooting. The Miami-Dade Police Department has arrested three men in that case, according to WPLG