The gruesome accident happened along the 1800 block of Colorado Boulevard Wednesday night at about 11:15 p.m.
"There were collisions with parked cars, there were collisions between the black Maxima that is unrecognizable," said Captain Lance Smith, Los Angeles Police Department.
Authorities said the accident was one of the worst they've seen. Body parts and car parts were scattered throughout the area, and a Nissan Maxima remained wrapped around a tree.
"There was, like, body parts almost on the floor. One guy's legs were cut off. One guy's arm was around his head ... broken and everything. One guy was under me yelling for help. I didn't know what to do," said Bryan Hammad, eyewitness.
Police believe the Maxima, a white Mitsubishi and another car were traveling westbound down Colorado Boulevard at a high rate of speed. The driver of the Mitsubishi slammed into a parked car, the Maxima hit a tree and the third car reportedly fled the scene. Many witnesses tried to help the victims, but there was little there could do.
"I tried to help, but some people dead, I couldn't do anything," said witness Arman Hakopian. He said because the Maxima was on fire, they focused on it first and did not see the car that fled.
While police are unsure how fast the cars were going, they said they measured 160 feet of skid marks.
Three people died on impact in the Maxima. Police said a pregnant woman, Cristyn Cordova, 19, was driving. Cordova, who was approximately eight months pregnant, died in the crash. Her sister, Toni Cordova, 16, was also killed.
Three men were also in the car. One of them, 19, Jason Timothy Gomez Hernandez, was killed. The two other passengers are in extremely critical condition, and authorities said if they survive, it would be a miracle.
The 19-year-old driver of the Mitsubishi, Rostislav Shnayder, was still on scene Wednesday night and was arrested on suspicion of murder.
Anyone with information is urged to call the LAPD at (877) LAW-FULL, or (877) 529-3855.
Eyewitness News reporters Melissa MacBride and Carlos Granda contributed to this report. The Associated Press also contributed to this report.