MISSION VIEJO (CBSLA.com) — The teen believed to have been the driver in a fiery Irvine crash that killed five other teenagers was often warned to slow down, a sibling of the youngest victim said Monday night.

Arlene Moreno tells KCAL9’s Stacey Butler that her 14-year-old brother, Brandon, and the alleged driver, identified by authorities as Bradley Morales, 16, were the best of friends.

“We trusted Bradley so much. I knew him since freshman year. My brother and him went out like every time and nothing ever happened. My mom trusted him with his life,” she said of Morales.

Brandon was among five teens killed early Saturday morning driving from Knott’s Scary Farm on the 5 Freeway south of Irvine. The vehicle they were traveling in veered off the road and onto an embankment.

Morales was the sole survivor, while Jennifer Campos, Jennifer Bahena, Matthew Melo, Alex Sotelo and Brandon Moreno died at the scene.

The cause of the crash remains under investigation, although the California Highway Patrol says speed may have been a factor.

“Every time. Every person who went into his car with him. Everyone told him to slow down,” Arlene said.

Moreno also said Morales recently bought the older-model BMW for $1,000. Investigators say he did not have a driver’s license nor a learner’s permit and that the vehicle was registered to an undisclosed family member.

“I love him, but I’m really mad at him because I don’t know what he was thinking. Speeding is not right,” she added.

Click here to donate to the Brandon Moreno fund.

RELATED STORIES:

More Details Emerge After Fiery Irvine Crash Kills 5 Teens

OC Students Mourn Classmates Killed In Fiery Crash

Vigil Held For 5 Teens Killed In Fiery Irvine Crash

5 Teens Killed In Fiery Crash On 5 Freeway In Irvine