ALTADENA, Calif. (AP) — A California man has been charged with stabbing his mother and uncle to death in an attack that the woman’s co-workers witnessed on a Zoom call, prosecutors said Monday.

Deputies responding to reports of a stabbing on March 22 discovered the man dead in the driveway of a home in the Los Angeles suburb of Altadena, according to Los Angeles County sheriff’s officials. The woman was found dead inside the house.

The victims were identified as Kenneth Preston, 69, and Carol Brown, 67.

“This is a horrific case in which the mother’s work colleagues witnessed part of the attack while on a Zoom call and called the authorities,” county District Attorney George Gascón said in a statement.

Authorities didn’t release additional details about the attack or what motivated it.

Deputies arrested Robert Anderson Cotton at the scene. The 32-year-old has been charged with two counts of murder with an allegation of using a knife as a deadly and dangerous weapon, prosecutors said.

It wasn’t immediately known if he has an attorney who could speak on his behalf.

Investigators said the three all lived at the house in the suburban neighborhood about 15 miles (24 kilometers) north of downtown Los Angeles.