Gruesome video shows the moment two vicious pit bulls mauled a “happy little” Chihuahua on the Upper West Side over the weekend — in what may be the second attack by the aggressive dogs.

Penny, a 16-pound Chihuahua mix and service pooch, now has two 6-inch scars across her slim body after one of the larger dogs ambushed her and chomped down on her at the corner of 86th Street and Columbus Avenue Saturday night, according to the sickening video.

Eventually, the rescue dog’s co-owner, Devon Allen, 40, was able to pry open the pit bull’s mouth with a man’s cane and pull Penny to safety as a bystander put the beast in a chokehold on the ground.

“There was a shocking amount of blood,” Allen, who shares Penny with his 38-year-old ex-girlfriend Lauren Claus, told The Post Tuesday.

“She’s a very small dog, and there was blood everywhere, all over my girlfriend and her pants, all over Penny, certainly on the ground. I can’t even think about what the cuts were like on her, I mean, this, this part of her skin was completely folded back and exposed.”

The clip later showed a man and woman strolling away with the two beefy pit bulls after the stunning attack, as someone can be heard in the background shouting to call the police.

The man who owns one of the pit bulls can be seen yanking the hair of the bystander on the ground, who was trying to break up the vicious dog attack in another video, which Penny’s owners gave to police.

Allen, a freelance lighting director, said he was walking the 10-year-old Chihuahua, and as they passed the two beasts, one initially lunged at Penny, but she escaped. That’s when the second dog pounced at the victimized pup before both pit bulls, at one point, had Penny in their mouths, he recalled.

The man who owned the pit bulls then delivered a chilling message to Allen.

“And as I’m trying to figure out what to do, and people are running from all over, the pit owner looks at me and says, ‘There’s nothing you can do,’” he said.

“Like, Penny is going to die and there’s nothing I can do to save her.”

Once Penny was freed, people from a restaurant across the street rushed to provide tablecloths to hold the tiny injured dog in while other bystanders got Allen a cab so he could rush to an animal hospital.

“I thought Penny was going to die,” he said.

When Allen called co-owner Claus, she was stunned.

“Honestly, I just stared at my boyfriend like, f–k, and he doesn’t know what’s going on because he didn’t hear the other end of the conversation,” the Fox Weather director told The Post.

She also rushed to the veterinarian to wait, calling it a “miracle” that Penny pulled through.

“She’s a happy little dog,” said Claus, who brings Penny work daily.

On top of the two 6-inch stitched-up tears on her upper back and her haunches, Penny also suffered numerous puncture wounds.

“She’s probably one of the most loved dogs around, because she just has so many people in our orbit that just love her,” Claus added.

“She’s just so incredibly loving. I’ve never had a dog so calm around everybody and everything, every situation, she is like a very steady presence in my life.”

This appears to be the second dog attack carried out by the pit bulls, according to a report.

Another Big Apple local, Lauren Block, told CBS News this week, the same two pit bulls mauled her two shih tzu mixes, killing one of them in Central Park in January.

City Councilwoman Gale Brewer, who represents the Upper West Side, called on the NYPD to remove the pit bulls from the home and place them in the care of Animal Care Centers of New York City for now — while also vowing to push legislation to address dog attacks.

“This was an assault,” Brewer said in a statement. “We need and deserve to feel safe in our community. We cannot let anyone terrorize neighborhoods, including dogs.

“The NYPD must be able to address an attack on a dog by another dog, and I will be introducing legislation to address such situations.”

Under current New York law, dogs are regarded as “property,” so a criminal case cannot be brought against dog owners whose pet harms another canine, leaving a civil suit as the only recourse.

Claus said she and Allen support new laws that would get dangerous animals off the streets and prevent bad owners from having dogs.

“We want is we want the owner to be held accountable,” she said. “There aren’t currently any laws that really help with dog-on-dog crime.”

Allen and Claus also called on the male owner of the pit bulls to be arrested after they claimed he assaulted multiple people during the chaos.

The NYPD said in an email that it received a report of harassment stemming from the canine commotion, noting a 64-year-old man who attempted to help Penny was shoved and his phone was thrown.

The man was not injured and his phone wasn’t damaged, cops said.