The area of Del Rosa Avenue where April was hit has no sidewalks and is packed with parked cars, forcing pedestrians to walk in the streets.
"It was like a car hit another car, it was so hard," said neighbor William Richardson.
Richardson said by the sound of the crash, he thought somebody had hit one of the parked cars.
"But instead it was her body that hit his truck so hard and then threw her at least 40 feet underneath the car that was parked here," he said.
Paramedics arrived and rushed her to a local hospital, where she was declared dead.
The victim's brother, Shawn Maher, said he found his little sister after she was thrown about 50 feet.
"She's my baby sister ... she's my baby sister, I love her," he said through his tears. "If anyone knows anything, please let us know."
April's brother said she was about to turn 18. She was attending high school in another state where she lived with her mother.
The two girls who were walking with April said the car was traveling so fast, and everything happened so quickly, that they did not get an accurate vehicle description. One witness said it was a late-model dark sedan, and another said it was a pickup truck.
"Investigators do believe the vehicle has right front-end damage to it," said Cindy Beavers, San Bernardino County Sheriff's Department.
Investigators say they may be looking for a full-size truck with an extended cab. They say it is possibly a Toyota and it would have that front-end damage.
Anyone with information is urged to call (909) 425-9793