The occupants killed were a male driver and two women passengers. Their identities were not known.
Three other victims were taken to a hospital and were listed in serious to critical condition. They included a 55-year-old man, 36-year-old woman and 6-year-old girl.
The crash, which happened about 7 p.m., forced the closure of eastbound lanes of the 134 Freeway at Colorado Boulevard.
The exact cause of the crash was not immediately known, but the California Highway Patrol said the SUV was eastbound on the 134 Freeway when a tire may have blown. Officials said alcohol was found at the scene and may have been a factor in the accident.
"The witness observed possible tire debris," CHP Officer Adam Eggleston said. "The vehicle lost control, began to flip, rotated approximately three times and a child was ejected.
Investigators said it appears the girl was not wearing a seat belt.
The SUV plummeted 75 to 100 feet to the road below, narrowly missing a passing car, officials said. Stunned witnesses rushed to help the five people still inside the vehicle.
Witnesses on Figueroa Street said it was a surreal scene as the SUV came flying over the edge of the freeway up above.
"It's like a movie, it's like a dream. It doesn't seem real," said witness Andrew Gutierrez. "You just turn around and there's dead people. You feel for them because you don't even know them, just know that they're dead. You just try to help somebody out."