John Winkler, 30, had just relocated to Southern California six months ago to pursue his dream of TV writing and producing after completing his education at the Seattle Film Institute.
On April 7, a deranged man with a knife held Winkler and three others hostage inside a West Hollywood apartment, stabbing two of them. When Winkler and an injured hostage ran out the front door, deputies opened fire, apparently thinking Winkler was the assailant.
Lisa Ostergren says her son's death is completely senseless.
"We're in shock and disbelief at what's happened because it never should have happened. Words really can't express how devastated we really are," she said.
"This has been my worst nightmare. I try to stay strong during the day for my family, but I cry at night. I don't sleep. I have nightmares about what happened to John. My whole world is just turned upside down."
Attorney Simeon Osborn, who is representing Winkler's family, questions how deputies could mistakenly shoot the men when they had a photo of the attacker.
Ostergren says her family wants to find out the truth.
"We want those officers to be held accountable for their actions and what they've done so no other family has to go through this nightmare and the pain that we're suffering right now," she said.
The family's attorney plans to file the claim in federal court, alleging the sheriff's deputies violated Winkler's civil rights by shooting and killing him.
Deputies said their description of the attacker was a white man with a thin build wearing a black shirt and Winkler was wearing a black shirt at the time.