Jacobson was found hanging from the ceiling.
Two school staff members got Jacobson down and called 911, Point said. Paramedics who responded performed CPR but were unable to revive her. Point said no suicide note was found but detectives believe she did take her own life.
"She appears to have committed suicide prior to the start of school at some point in time," he said.
Students in the room next to Jacobson's described seeing two students storm into their class and run straight toward the teacher. The teacher ran out of class and screamed when she entered Jacobson's room.
"Right away we knew something really horrible had happened," freshman Tessa Hoover told the Orange County Register newspaper.
Students were dismissed for the day at 11 a.m. and crisis counselors were made available on campus, said Assistant Superintendent Kevin Lee, of the Placentia-Yorba Linda Unified School Districts. A crisis intervention team planned to remain on campus for the rest of the week.
Jacobson, of Anaheim, had a bachelor's degree in ceramics and glass, and art education, according to a biography on a website for a children's art camp at Cal State Fullerton. She also had a master's degree in educational leadership. She had taught at El Dorado since 2008.
"My goal every summer is to give campers an experience they will always remember, and to send them home with art work they will be proud of for years to come," she said in the bio.
On her profile page at El Dorado High School's website, Jacobson smiles in a photo near the words, "Today is a great day to take a picture!"
Several students posted tributes on Facebook and Twitter, crediting Jacobson with inspiring their interest in photography and being a caring teacher.