Robert Anderson Cotton has been charged with the killings and the District Attorney's Office is seeking $4 million bail.
Part of the attack Monday afternoon was caught on a Zoom call by a person who promptly called 911 with a report of what at first appeared to be a kidnapping.
Police say Cotton fatally stabbed his mother, 67-year-old Carol Anne Brown, and her brother, 69-year-old Kenneth Wayne Preston at the home.
RELATED: Two killed in attack partially witnessed on Zoom
2 fatally stabbed at Altadena home in incident partially witnessed on Zoom, officials say
Brown was on a Zoom call with a colleague who saw the initial attack on Preston unfolding and called it in as a potential kidnapping.
Preston was dragged outside the home and responding officers found his body on a driveway, though it is not clear if the fatal attack happened inside or outside the home.
After finding Preston's body outside, the officers went inside and found Brown.
As detectives were investigating, Cotton drove up to the home in a car belonging to one of the victims. He was quickly taken into custody.
Neighbors of this quiet community are stunned.
"This is just bad," said neighbor Darlene Thomas. "You live here and you don't expect to have tape and helicopters, and this. Somebody is destroyed, multiple people are destroyed by this."
A motive for the attack remains under investigation.