The horrible wreck happened in Winchester Thursday night at the intersection of Winchester Road and Keller Road.
The CHP says a black GMC Sierra ran a red light and then slammed into the side of a white Nissan Titan, which had the three high schoolers inside.
"It's sad that something tragic like this had to happen after such a great day. I mean, you finish high school, and then... it's just a lot," said Nadia Petrosius, a friend of the victims.
Friends and classmates of the victims have been coming to the accident scene all day Friday to leave flowers and other items at the memorial.
"They're all great people. I knew the driver and his sister best, but their whole family is very warm hearted," said Petrosius.
There is no indication that drugs or alcohol played a factor in the crash. The unidentified 30-year-old man driving the black truck may have just ignored the light completely.
Petrosius said it is not uncommon for drivers to run the red light at the intersection without hesitating.
"I mean, all the time, when you come up to this light you have to pause an extra two or three seconds just to see if someone's going to run it," said Petrosius.
The CHP says charges on the driver of the black truck, who is also in the hospital, are pending the completion of an investigation.
"Obviously, our investigation will determine what level this will reach, if it will be gross vehicle manslaughter if there's reckless driving or other circumstances that could dictate as far as the case," said CHP Officer Luis Godinez.