Updated

One of two identical twins was among 10 people killed on a Northern California freeway when a truck slammed into a bus carrying dozens of high school students on a college tour, a family member said Friday.

Marisa Serrato, 17, has been missing since Thursday evening after the FedEx tractor-trailer hit the bus carrying 44 high school students headed to tour Humboldt State University, said her brother Miguel Serrato, 23.

The other twin, Marisol Serrato, was on a different bus that wasn't involved in the crash and made it safely to the school.

The family had no word on Marisa for nearly 24 hours before dental records confirmed she was among the dead. Miguel Serrato said Marisol called their father Friday evening after going to see her sister's badly burned body.

"Marisol is devastated," the tearful brother said. "She thinks it's her fault, that it was her idea to go look at the university."

The crash happened near Orland, a small city about 100 miles north of Sacramento.

Marisol was accepted to Humboldt State University, while Marisa was waitlisted there. The two seniors from Norte Vista High School in Riverside decided to check out the campus.

"My sisters are real religious, smart, A students," Miguel Serrato said. "They were going to get their high school diploma; they were looking toward the future."

Serrato said his family learned about the crash while celebrating their father's 65th birthday. They spent a sleepless, agonizing night trying to learn the fate of Marisa, or "Marisita" as the family calls her. He said she was the baby of the family because she was born five minutes after her identical twin.

Another Norte Vista student also was on the bus that crashed and was in stable condition at a hospital.

Humboldt alumni Michael Myvett, 29, and his fiancee, Mattison Haywood, who were chaperoning, also were killed. Myvett was a therapist at an autism treatment center.

"He just died," his grandmother Debra Loyd said, her voice breaking with emotion in the early afternoon Friday. "They have already confirmed it."

Myvett's manager Kyle Farris said he was "extraordinary," and that he connected with their children "on a level few others could, and he contributed to their wellbeing in such a positive and profound way."

"He will be greatly missed," Farris said.

A Facebook photo shows Haywood flashing a shining diamond engagement ring on her finger and kissing Myvett in December near the Louvre Museum in Paris.

Both drivers were killed, along with three adult chaperones and five teenage students, according to the California Highway Patrol, which reached the scene shortly after the 5:30 p.m. accident about 100 miles north of Sacramento. Rescuers said the bodies were mostly at the front of the bus, or outside on the ground in front of it.

Miles Hill, a senior at Renaissance Arts Academy in Los Angeles, was one of dozens of students injured in the collision. Like other students on the burning bus, Miles smashed out windows to escape the flames, The Los Angeles Times reported.

His father, Gaylord Hill, told the newspaper his son is hospitalized in serious condition at Enloe Medical Center in Chico with burns, lacerations and an ankle injury.

"He's not a person that asks for help,” Hill said of his son. “But he told me, 'I want you guys up here. I need you guys up here.' So psychologically, he's really fragile."

The CHP and the National Transportation Safety Board were investigating, but warned it could take months to conclude what happened.

Mark Rosekind, an NTSB member, said Friday that the agency would be gathering information over the next one to two weeks. He said it will review whether the stretch of California freeway where the bus was struck should have had a barrier along the median to prevent head-on collisions.

The Associated Press contributed to this report.