The 18-year-old high school student perished while helping save fellow passengers after a FedEx truck crashed into the bus they were riding on a highway near Orland, Calif., according to officials from Jimenez's high school.
Four other students, three adults and both the bus and FedEx drivers died in the crash.
Jimenez, who was a student at Animo Inglewood Charter High School and would have been the first in his family to attend college, reportedly "busted open a window at the front of the bus as it was filling with smoke and people were getting burned," according to a statement from school Chief Executive Marco Petruzzi. "He started lifting kids out in an effort to save them."
"Ismael will forever be remembered as someone who forever affected the lives of young people he barely knew. He was indeed a hero," the statement continued.
"It's been very hard," Jimenez's sister Evelin told CBS-LA, "because you go to sleep thinking when you wake up, you'll see him. And I haven't seen him. So it's very difficult."
"He went ahead and saved others before he saved himself, which is, to me, beautiful," she said.
Jimenez's family told NBC-4 that he was an honor student and wanted to become an artist. The bus, full of high school students, had been traveling back to Los Angeles after visiting the campus of Humboldt State University in northern California.
A memorial fund has been set up by Jimenez's family.