VALLEY STREAM, Long Island (WABC) -- One man was killed, and three children shot when a gunman opened fire on an illegal party in Valley Stream late Monday night.
The crime scene stretched about three blocks along Ocean Avenue at 131st Avenue.
Nassau County authorities say Tuesday that a 20-year-old Brooklyn man was shot in the chest and pronounced dead.
A 12-year-old boy standing in the doorway was shot in the left upper shoulder after a bullet went in and came out of his back.
Two other boys, both 17 and both from Elmont, were also struck. One was hit in the rear of his leg and the other in his knee.
A fifth person suffered a laceration to her hand during the chaos that followed the gunfire.
WATCH: Nassau Co. police provide update on Valley Stream shooting
The gunman, described as a man wearing dark clothing, ran away after the shooting. He is believed to have fired eight shots from a semi-automatic .380 caliber weapon.
Around 100 people attended the party which police say was illegal because the organizers were charging admission and serving alcohol and possibly liquid marijuana to minors.
The owner of the space said the party organizers were not supposed to be serving alcohol and she was distraught over the outcome.
"The person that was struck took refuge inside of my event space, unfortunately I heard that he didn't make it, so my condolences," said property owner Deborah Young.
One witness who was at the party told Eyewitness News that it went from calm to chaos.
"I don't know how it got violent, I don't know if it was an altercation," Keith Joseph said. "It was a quiet peaceful night, maybe a little bit of music, not too loud, no violent music, no type of energy like that, we're only here to have a good time at the end of the day. Next thing you know, a good time turned into a bad night. And they start getting a little violent."
Neighbors say they have been concerned about the amount of people coming and going and whether or not the party space is legal.
"Most of the time, fighting, people are very upset around here," neighbor Sanny James said.
Nassau County authorities vowed to crack down on the parties after a flier for this party circulated on social media.
"We will be moving our Operation Overwatch into the community, we will make sure it's up and down the border with New York City and Nassau County," Nassau County Police Commissioner Patrick Ryder said.
So far, no arrests have been made.
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