1 dead, 11 injured in shooting in Brownsville section of Brooklyn Shots rang out just before 11 p.m.

Gunshots rang out at a neighborhood event in the Brownsville section of Brooklyn, New York, on Saturday night resulting in the death of one person and injuries to nearly a dozen others, according to the New York Police Department.

The shooting took place just before 11 p.m. at Brownsville Playground, a large park with basketball courts and athletic fields, during an annual event called Oldtimers' Day which has been held since 1963. The event was being cleaned up when the incident occurred.

Police said a 39-year-old man was struck by gunfire and pronounced dead at a local hospital. He was shot once in the head, according to the NYPD.

The victim has been identified as Jason Pagan, 38, according to a police source.

There were 11 other people who were shot and transported for treatment -- seven men and five women. One of those victims is in serious condition.

They ranged in age from 25 to 55 years old, the police source said.

New York City Mayor and 2020 presidential candidate Bill de Blasio tweeted, "We had a terrible shooting in Brownsville tonight that shattered a peaceful neighborhood event."

Mayor De Blasio gave a press conference on Sunday morning, in which he said that 100 NYPD officers were at the event when the shooting occurred.

"I want to thank the NYPD for a swift response, which unquestionably helped to make sure that those who were struck were saved," the mayor said.

"I want to make really clear this tragedy does not define Brownsville does not define the people Brownsville," he added.

The Old Timers' Day event has been held since 1963, and was sponsored by Council Members Inez Barron and Alicka Ampry-Samuel, who represent the area. There were about 2,000 people in attendance, according to the police source.

Samuel, who was at the event Saturday evening, tweeted in response to de Blasio, "One of the worst experiences of my life. How does such a beautiful and peaceful event become overshadowed by tragedy in seconds? We have to do more."

No one has been arrested. Police are looking for two shooters who used two guns. One weapon has been recovered as of Sunday.

Brownsville is known as a dangerous neighborhood in Brooklyn, though like all of New York City, crime has declined significantly in recent decades.

As of July 21, there had been six murders in the 73rd precinct, which includes Brownsville, so far this year, according to NYPD statistics. There have been 52 murders in all of Brooklyn so far in 2019, with only the 75th precinct (7) and 79th precinct (8) having more murders than Brownsville. The 75th precinct patrols East New York and the 79th precinct patrols Bedford-Stuyvesant, both neighborhoods near Brownsville.

Police are asking for anyone who has video from the event and there during the shooting to hand it over to authorities by calling 800-577-TIPS.

ABC News' Alex Faul, Aaron Katersky and Christopher Donato contributed to this report.