Parent Gloria Sanchez said her daughter heard the gunshots from inside the party.
"They said that they heard some gunshots, and they all just dropped to the floor. They didn't know exactly what had happened, but they did hear some gunshots," Sanchez said. "It's scary, it's a Venice High prom after-party, and there's so many excited kids in there, and for something like this to happen, it's just sad."
Police said a 21-year-old victim is in critical condition. The second victim was grazed by a bullet and is expected to survive.
Police are searching for the shooters. Anyone with information is urged to call (877) LAPD-24-7.