A key witness scheduled to testify this week in the involuntary manslaughter trial involving a Northern California warehouse fire that killed 36 people has died in a car crash, prosecutors told a judge Monday.

Alameda County prosecutors had planned to call Robert Jacobitz to testify this week in the trial of Derick Almena and Max Harris, each charged with 36 counts of involuntary manslaughter in connection with the Dec. 2, 2016, fire in an Oakland warehouse during an unpermitted music concert.

Prosecutors say they turned the warehouse into an unsafe entertainment venue and residence.

Alameda County deputy district attorney Casey Bates told jurors last week that Jacobitz was an unlicensed contractor who performed inexpensive work at the warehouse soon after Almena rented it in November 2013.

Prosecutors allege that Almena, 49, stuffed it full of highly flammable furniture, pianos and other material and failed to provide smoke detectors, fire alarms, sprinklers and other required safety equipment. Prosecutors say Harris, 29, helped Almena convert the warehouse, collect rent and schedule concerts.

Bates said during opening statements last week that Almena turned to Jacobitz for inexpensive help with the warehouse's conversion after another contractor told Almena it would cost at least $5,000 to install a fire door and new stairs to the second floor.

Prosecutors have also said Jacobitz performed electrical work at the warehouse.

Investigators looked closely at the warehouse's electrical system before concluding the cause of the fire could not be determined.

Testimony in the involuntary manslaughter trial of Derick Almena and Max Harris started Monday in Oakland with a tearful mother of one of the victim's telling the jury about her daughter's last moments.

Carol Cidlik said she received a text from her 29-year-old daughter Nicole Siegrist at 11:23 p.m. on the night of the fire.

"I'm gonna die now," Nicole texted her mother. Investigators said Siegrist and the 35 other victims all died of smoke inhalation minutes later.