Seven men and five women, ages 21 to 55, were among the victims, according to police.
The shooting erupted just as the crowd at the annual Old Timers Event in the Brownsville neighborhood was beginning to disperse Saturday, witnesses said.
"There were a lot of people just chilling and having a good time," Kaseem Collins, 19, told the Daily News. Then, when shots rang out, "we all started running," he said. "I ran as fast as I could away from everyone. I thought I was going to get shot."
"I heard shots, and I saw a stampede running toward me," Diamond Perez, 38, told the newspaper.