Fontana police and San Bernardino deputies executed an exhaustive 28-hour search using various resources including officers in the sky and on the ground. They even utilized a helicopter equipped with heat-seeking equipment to track down the animal.
The order given to crews throughout the search was shoot to kill.
The lion killed a 100-pound German shepherd in the backyard of a home in the 4100 block of Fox Borough Drive on Wednesday. The dog's owner, Jonathan Slater, said the lion was three times the size of his dog, Princess.
Slater's father said when he went to check on Princess, the lion displayed very aggressive behavior toward him.
Responding officers came face-to-face with the animal outside Slater's home.
"The mountain lion was in a position where it could immediately pounce on the officer within 10 to 15 feet. The officer retreated and fired several rounds at the mountain lion. We are not sure if the lion was hit," said Fontana Police Chief Rodney Jones.
Authorities said the animal is different than others they've dealt with in this area.
"The officers fired some shots to scare the animal away but it came back a total of four times. That's considered very unusual behavior, and so we took necessary precautions to protect our residents," described Martha Guzman-Hurtado with Fontana police.
Jones said he believes that confrontation with the officers caused the lion to hideout deep in the canyons. He said officers will continue to routinely patrol the area.
Though the search has been suspended for now, police are still urging residents to remain vigilant of their surroundings. Police have called the lion an imminent threat to public safety.
Knowing a killer mountain lion is still on the loose is unnerving to residents.
"It's obviously scary to go outside by yourself. I can't even go outside my house, knowing there's a mountain lion around," said Fontana resident Seline Bacallao.
Residents are also encouraged to keep their pets indoors and remember that mountain lions are most active from dusk to dawn.
If you spot the lion, you're urged to dial 911 immediately.