INDIO, Calif. -

The district attorney alleges Michael John Franco used a Toyota Prius and a box cutter as weapons in commission of the murder of his girlfriend.

On Friday, Franco plead not guilty in an Indio courtroom.  The body of a popular local math teacher was discovered in Indio early Monday morning.

The Riverside County Coroner's Office released the autopsy report and identified the victim as 41-year-old Jill Grant. Grant taught math at Palm Desert High School starting in 1998, according to the Desert Sands Unified School District website.

Jill Grant

(Photo Courtesy of dsusd.k12.ca.us)

A day after Grant's body was discovered, officers with the Indio Police Department arrested her boyfriend, 42-year-old Michael Franco. A murder charge was filed against Franco and he plead not guilty on Friday afternoon at the Larson Justice Center. A public defender was appointed to him.

Franco is being held on $5 million bail.

Franco also faces a felony count of being a convicted felon in possession of a firearm and carrying a loaded firearm, and a sentence-enhancing allegation of using a deadly weapon in the commission of a felony, according to CNS. 

Indio Police Department spokesman Ben Guitron said Grant sustained
``multiple injuries,'' including fractures and she died from trauma. No additional information has been released regarding how she was killed.

Police said Franco lived with Grant in the  84400 block of Onda Drive. Authorities found evidence at the home that led them to believe Franco was a suspect in her death.

Franco was arrested after police analyzed information on his cell phone. Officers found him driving his car in the 47200 block of Heliotrope Drive in Palm Desert after tracing his cell phone, according to Guitron.

Franco was taken to the Riverside County Sheriff's Jail in Indio around 2 p.m. on Tuesday.

Grant's body was discovered around 6:30 a.m. in a dirt area near the intersection of  Avenue 42 and Golf Center Parkway on Monday. Investigators had the area sealed off for several hours.

According to the Desert Sands Unified School District website, Grant grew up in the Santa Rosa Mountains above Palm Springs and attended Palm Desert Middle School and Palm Desert High School, graduating in 1990.

Grant attended College of the Desert, then transferred to Cal State San Bernardino, where she majored in mathematics. She taught math at Palm Springs High School for three years, starting in 1995, and began teaching at her alma mater in 1998.

"It is just a tragedy and it is a shock.  We are extremely saddened and devastated by the news.  She is a beloved teacher by her students and faculty and staff at Palm Desert High School," said Sherry Johnstone, assistant superintendent of personnel for D.S.U.S.D. "We are all grieving for her family."

The district is providing counseling for students at the return of winter break.

"When there is a tragedy, we have a team of counselors that go to the school and help students and staff," Johnstone said.

People have started placing flowers on the grounds of Palm Desert High School as a memorial to Ms. Grant.

Franco is due back in court on January 6, and his preliminary hearing is set for January 8, according to court documents.

The Indio Police Department is asking anyone with information about the incident to call them at (760) 391-4057 or call Coachella Valley Crime Stoppers at (760) 341-STOP with anonymous information.

Continue to follow KESQ/CBS Local 2 News for the most current information as the investigation unfolds.