Anila Baby, 33, is accused of strangling and stabbing Ann Mary Mathew in San Jose before allegedly killing Anjana Hari in Milpitas about 90 minutes later, according to prosecutors.
Baby faces two counts of first-degree murder and a potential sentence of 50 years to life if convicted.
"Both women were mothers. They are residents of our community, and their families are suffering terribly from the ultimate question of 'Why would someone do this?'" Deputy District Attorney Marisa McKeown said.
McKeown said prosecutors believe the killings were deliberate.
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"These are extremely serious charges. We believe that these were willful, premeditated and extremely violent crime scenes," she said.
According to investigators, the first killing occurred on Aug. 28 in San Jose at Mathew's home on Linda Vista Street.
Witnesses reported that an unexpected guest arrived at Mathew's door. Prosecutors said Mathew was later found by her husband inside the home. Investigators said she had been strangled and stabbed and was left in a pool of blood.
Shortly afterward, Hari was called to the parking lot of her apartment complex in Milpitas, according to court documents. When she walked in front of a vehicle, prosecutors said the driver accelerated and struck her, killing her.
Investigators later linked the two killings and identified Baby as the suspect.
"Through a combination of forensic investigation and followup interviews, we were able to charge the defendant with both of those murders and do believe that they were committed within about an hour and a half of one another," McKeown said.
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Police said Baby was covered in blood and had injuries to her face when she was arrested after allegedly attempting to flee the Milpitas scene with her vehicle to a nearby parking lot.
Investigators also said video recordings from Mathew's home were deleted during the time of the attack, but Baby's sandals were seen outside the residence.
McKeown said the victims' families continue to struggle with the loss of the two women.
"Really, the biggest heartbreak of this case is these families were best friends and want answers as to why someone could do this to their friend. So, I hope we can provide answers as we investigate this case," she said.
On Sept. 1, murder charges were filed against Baby for the Milpitas case, according to the Santa Clara County District Attorney's Office. On Tuesday, Baby was also charged in the San Jose homicide.
Baby is scheduled to return to court Nov. 17 at 9 a.m., when she is expected to have the opportunity to enter a plea. She remains in custody without bail.
Bay City News contributed to this report.