A woman punched a mountain lion and tried to pry open its jaws after it attacked and killed her dog in her back garden, officials said.
The schnauzer, called Pumbaa, woke up his owner at 2am on Thursday to go outside.
But the woman, who has not been named, opened the door and spotted a mountain lion.
The dog owner's brother, only identified as Brian, told ABC7 Los Angeles: "She figured it had to go to the bathroom and opened the door.
"I think she went out first, and she saw the mountain lion and her dog charged under her legs toward the mountain lion, and the mountain lion snapped it up."
The owner reportedly then tried to fend off the animal by punching it and trying to pry its jaws open.
Brian added: "She jumped on the mountain lion and tried to pry its jaws open to save her dog because she loves her dog so much.
"The whole time, she could hear her baby dying."
After attacking Pumbaa, the lion growled at the woman and she managed to escape.
The Southern California woman managed to get away with only a minor cut, police Sgt Keith Eisenhour told KNBC-TV.
Somewhere in the hills above Simi Valley this guy is lurking. The mountain lion killed a dog last night and tonight stared at a dog inside a home for about 45 minutes. The neighborhood is understandably on edge. We’re live at 11 @ABC7 pic.twitter.com/IZ2UcGi4PP— Jory Rand (@ABC7Jory)December 6, 2019
He added: "She obviously cared about her dog very much, as all dog owners do.
"She tried to fend the animal off by punching it, elbowing it and tried to pry its jaws open."
Police said it is believed the animal fled back into the hillsides around the area.
The attack happened about 35 miles northeast of downtown Los Angeles in a neighbourhood next to wildlands.
It followed a report that another dog was injured by a mountain lion in the same area late Wednesday.
According to ABC7, one family said their 16-year-old daughter was home alone with the family dog when a lion came to the back garden, stood against the glass door of the house and looked inside.
ABC7 Eyewitness News reporter Jory Rand tweeted: "Somewhere in the hills above Simi Valley this guy is lurking.
"The neighbourhood is understandably on edge."
Many mountain lions in the area and in wildlands to the south are being studied by biologists with the Santa Monica Mountains National Recreation Area to determine how they survive in habitat increasingly fragmented by development and freeways.
Police Commander Adam Darough said the mountain lion seen Wednesday had a tracking collar but officers could not see if the animal that attacked the dog had a collar.
Ana Beatriz Cholo, a spokeswoman for the national recreation area, told the Star that the animal was not one of the mountain lions being tracked with a working collar but may be an adult female that was living in the area before her collar stopped working.
The National Park Service installed a tracking collar on that female in 2014 when she was 4 or 5 years old and was mostly living around the highest peak in the Santa Susana Mountains.
Now, she would be fairly old for a female mountain lion in the wild.
Additional reporting by agencies