The child suffered injuries to the neck as a result of the attack, according to the Orange County Fire Authority who said the family of six was walking in the park with the 3-year-old in front of his father when the feline came out of nowhere and grabbed the child by the neck.
The father threw a backpack at the mountain lion, at which point the animal dropped the child in lieu of the backpack and jumped up a tree, the Orange County Fire Authority said.
The child was taken to a local hospital and is said to be in stable condition.
The incident occurred at about 4:13 p.m. on Portola Parkway.
The park was evacuated as park officials monitored the mountain lion in the tree. California Fish and Game officials responded to the scene. At about 5:30 p.m., officials on scene confirmed the mountain lion had been killed.