The teenager who was fatally shot has been identified as Dominique Peatry of Lancaster.
The initial calls came in as neighbors complained the party was getting out of hand and said there was excessive noise, but then a fight broke out before officers arrived.
"When the shots were fired, everybody dispersed. Kids started hiding in everybody's backyards. Some of the individuals in the back of police cars were some of the people in our backyards," said Lancaster resident Steve Nichols.
Officials said the shooting started inside a residence on Nugent Street and moved out onto the street. It's not clear what triggered the fight, but authorities confirm that multiple weapons were used in the shooting.
A man who did not want to be identified said his step daughter was shot in the back.
"I'm just trying to find out what happened to my stepdaughter," he said. "Somebody just came over here shooting like this. It was nothing but a kids' party, so we don't understand why someone would do this."
Multiple shooters may have been involved.
"The physical evidence at the scene would indicate that there was more than one gun involved and what we're looking for is at least one lone male who appeared to be in the company of two or three others when he arrived. Whether or not they're physically involved remains to be seen," said Los Angeles County Sheriff's Department Lt. Patrick Nelson.
The victims with gunshot wounds were taken to Holy Cross Hospital in the Antelope Valley. Officials say the victims include three females and four males, whose ages range between 13 and 26 years of age.
Their identities are being withheld pending notification of relatives and because of their ages.
Neighbors in the area said this isn't the first time they heard gunfire on this street. Last week, residents said they heard several gunshots, and police were called but no one was injured.
Some are speculating that Sunday's shooting may be a retaliation for the previous incident.
Residents said they heard at least 15 shots fired and saw several people running down the street after the party dispersed.
"By the time I looked out my window, there were at least 12 or so kids scattering everywhere," said a resident who did not want to be identified. "By the time I got down there, there was a young male coming out of my backyard."
Authorities said witnesses are not being forthcoming with information, but because an estimated 40 people attended the party, police are hopeful that they can garner enough information to obtain the descriptions of the gunmen.
The Associated Press contributed to this report.