'Terrified' Family Gets Sad News: Missing Twin Is Dead

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To answer or not to answer? The decision was torture every time the phone rang at the home of Marisol and Marisa Serrato.

Now the terrible wait is over. Marisa's family confirmed Friday night to NBC Los Angeles that she was killed when a FedEx truck plowed into a bus carrying high school students on a college tour to Northern California.

Marisol and Marisa — 17-year-old twin sisters from Riverside — were among the dozens of Los Angeles-area high school students on three buses when the collision occurred Thursday, killing at least 10 people.

The girls were nearly inseparable, but this time took different buses. Marisol's bus wasn't involved in the wreck.

"You want to answer it to see if it's good news, but you're terrified that it could be bad news," their younger sister Christina told NBC News on Friday.

Whenever the phone rings, "it's horrible," she said.

Both sisters had been accepted to numerous colleges, but they wanted to go to the same school. So they decided to skip their prom Friday night at Norte Vista High School and make the trip to check out Humboldt State University, 525 miles north in Arcata, where Marisol had been accepted and Marisa was on a waiting list.

Marisol Serrato, left, and Marisa Serrato, right, both 17 (with their sister-in-law Ivette Serrato at a wedding in 2013), were part of the group of high school students on the bus trip Thursday. Marisol wasn't in the accident, but Marisa remains unaccounted for.Miguel Serrato via AP

Authorities said Friday that five students were killed in the fiery crash — but four of them remained unidentified, and wherever they call, no one can tell the family where Marisa is or whether she's even alive.

The family has been frantic since they learned about the crash while they were celebrating their father's 65th birthday — especially after the coroner's office called Friday to ask for Marisa's medical and dental records.

The Serratos are trying to stay positive. But it has been especially hard for Marisol, who "believes that it's her fault because it was her idea to go check out that university," her brother, Miguel, 23, told The Associated Press.

"She's devastated right now," he said. "I told her to keep her head up and have faith in God."

I just know that God has them safe. We love them a lot and we're waiting for them to come back," the twins' younger sister Clara Serrato told NBC4.

The mother of Marisol and Marisa Seratto says she's desperate to learn what happened to Marisa.NBC Los Angeles