FONTANA ( — An aggressive mountain lion killed a family dog early Wednesday in a north Fontana neighborhood.

Officers responded to the 4100 block of Foxborough Drive for a report of an attack against a 100-pound German Shepherd, Fontana police said.

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The owner, Jonathan Slater, heard his 5-year-old dog named Princess in distress around 3:30 a.m. and went outside.

Slater told CBS2’s Tom Wait that Princess was “a close part of the family, especially to my father.”

The grieving dog owner said, “I never thought a mountain lion could jump over a fence like that.”

He found the “large mountain lion standing over his deceased pet displaying a very aggressive behavior toward the resident,” spokeswoman Martha Guzman-Hurtado said.

When officers arrived, they encountered the animal in the front yard, shot at it and it ran into a nearby canyon.

The aggressive lion was not scared by the gunfire and returned moments later.

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“The mountain lion kept returning and coming towards the officers in front of the residence a total of four times before disappearing into the canyon,” Guzman-Hurtado said. “There is no evidence that the lion was ever struck by any rounds.”

Police have deemed the animal an imminent threat to public safety.

“Our intent is to secure the perimeter around the homes and make sure that we can either scare the mountain lion far enough away or, if we’re able to locate it, then, you know, since it has been deemed a threat, then we will have to probably shoot it,” Guzman-Hurtado said.

Fish and Wildlife, the Fontana Police Department and a helicopter are patrolling the area using infrared equipment to “pick up the heat signature of the animal.”

Resident Ashley Meneses said many neighbors were rattled by the attack.

“Everybody is very rattled, everybody is shaken up,” Meneses said.

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Residents are encouraged to remain vigilant, keep pets inside and call 911 if you spot the mountain lion in your neighborhood.