Mission Viejo resident Madison Smith was with her two children, 5 and 7, on Sunday. Smith says they were just 10 minutes into their hike when it happened.
A mountain lion came out of the bushes. Smith says her daughter noticed it first.
"She jumps up and says 'Kitty,' she was so excited, and I go, 'No, no!'" said Smith. "My son moved back towards me, and as soon as he did that the lion got in the crouching position to pounce."
Signs around the park tell people to stand your ground, throw rocks and shout. Smith says it was another hiker who did just that to try to get the lion to go away.
Smith says then another, even younger child came running up the trail, and she thought the lion was going to attack him.
"And I had to tell him to stop running," said Smith. "And I was very scared for him, thinking that the lion was going to chase him, because he's just a little boy."
Smith called 911 and California Fish and Wildlife personnel arrived. They found the mountain lion, and because it was acting aggressively and showed no signs of fear, they shot it.
About 10 years ago, a 35-year-old man was killed by a mountain lion in the same park.
Game wardens were searching for a mountain lion near the city of Orange on Monday.