Smiling Sisters Kitty & Cookie Face New Twist in Mom’s Brutal Murder

From the Desk of Detective Brian Colwel: My Firsthand Account of the Diaz Sisters Stabbing Case in Del Rio

I’ve been a detective in Texas for over two decades, and I’ve seen my share of senseless violence. But the case of Caro Peña still sits heavy with me. As one of the investigators who responded and helped piece together the evidence in those critical first hours, I watched a bright summer day in Del Rio turn into a nightmare that claimed the life of a 32-year-old mother of five. What started as a reported stabbing led us straight into a brutal, video-documented attack involving three young women—sisters Cookie and Kitty Diaz, and their friend Keandra Faz. I’m putting this down now, while details are fresh, because the public deserves to understand how quickly things escalated and why this one feels so personal.

Let me take you back to June 25th. We got the call that a woman had been stabbed and was in rough shape at the local hospital. When I arrived, doctors were fighting to stabilize Caro Peña. She had been stabbed three times: twice in the back and once in the stomach. The wounds were deep and vicious. She was airlifted to San Antonio, but she didn’t make it. Those hours between the attack and her death are etched in my mind—knowing we had suspects moving fast while a mother of five clung to life.

From the hospital, our team moved quickly to the scene. The address pointed us next door to where 19-year-old Keandra Faz lived. She was cooperative at first, telling us that Caro Peña had shown up “looking to start a fight.” That claim raised immediate questions. In my experience, people involved in violence often point fingers to shift blame. We didn’t rely solely on her words. What changed everything was the doorbell camera footage from the property where the altercation happened.

I watched that video with my own eyes. A black pickup truck pulls up—Caro Peña behind the wheel. Tension is visible almost immediately. Then a black Chrysler arrives. Out step Cookie and Kitty Diaz. Cookie, whose full first name is Amaya, is holding something in her right hand. Even on the grainy footage, it was clear it was a knife. She approaches Peña directly. The first strike lands in the back. Blood blooms across Peña’s shirt. Kitty and Keandra join in, physically assaulting her. It was chaotic, brutal, and over in moments that felt eternal on replay.

Cookie was wearing a red tank top and blue jeans. Kitty had on a pink tank top with blue jeans. Those clothing details became crucial later. After the attack, the three fled. Peña somehow got herself help, but her injuries were too severe. In my career, I’ve seen knife attacks up close—they’re intimate and messy. You feel every impact. Retired homicide detective Phil Waters, who consulted on coverage of this case, put it perfectly: blade work is personal. Unlike a gunshot from distance, you’re right there, breathing the same air as your victim.

Our investigation moved at lightning speed—something I’m proud of. Within about two hours of the initial hospital call, we tracked the Diaz sisters to another residence across Del Rio. Cookie’s car, the one allegedly used to get to the scene, was parked right out front. When we made contact, the change in appearance was obvious. Both sisters had showered; their hair was still wet. They were no longer in the clothes from the video. That wasn’t coincidence. It screamed evidence tampering, especially for Kitty, who now faces that additional charge alongside murder.

I remember the arrest footage that went viral. Cookie smiling at the camera, even cracking a joke. At that point, Caro Peña was still fighting in the hospital. That smile haunts me. In my years interviewing killers and suspects, I’ve seen all kinds of reactions—defiance, shock, tears. But laughter right after a deadly stabbing? It doesn’t sit right. As Waters noted in discussions around the case, it can point to deeper issues: someone who feels justified or, worse, someone who enjoyed the act. Sociopath or psychopath—the labels matter less than the cold reality that a life was taken.

Let’s talk about the people involved, because that’s where this case gets even more chilling.

Caro Peña was no stranger to any of them, according to our chief. She was a devoted mom. Just weeks earlier, she posted videos of family outings by the water—normal, happy moments with her five kids. Her friends described her as a fighter who stood her ground even while bleeding. That resilience makes her loss sting more. Five children now grow up without their mother because of a confrontation that spiraled out of control.

On the suspects’ side, the contrast is jarring. Kitty Diaz, 21 years old, had built her social media around being a loving mom to her four-year-old son. Video after video showed her calling him her “entire world.” I’ve reviewed enough digital footprints in cases like this to know social media is a highlight reel, not the full story. But it’s still jarring to see a young mother accused of participating in such violence. Cookie, her sister, allegedly brought and used the knife first. Keandra Faz, the youngest at 19, allegedly joined the fray and provided that initial statement about Peña looking for trouble.

All three were unemployed and are being held on $5 million bonds. The speed of the arrests—under two hours from hospital notification to custody—came down to solid police work, neighbor tips, and that doorbell camera. We didn’t leave many stones unturned in those early hours.

As a detective who sat through the briefings and reviewed the evidence, I can tell you the law of parties in Texas is going to play a major role here. Even if only Cookie delivered the fatal strikes, Kitty and Keandra’s active participation in the assault ties them all together. You don’t get to stand by or join in and claim you’re innocent of the outcome. That’s how collective violence works in the eyes of the law.

Motive remains a big question mark, though it’s not required for conviction. Was it drugs? Money? Some deep interpersonal beef? Waters speculated it could involve any combination of the classic drivers—sex, drugs, money—or simply raw personal turmoil between women who knew each other. Faz’s claim that Peña arrived looking for a fight might be tested in court, but the video tells its own story. Self-defense? Highly unlikely when three people converge on one with a knife.

The tampering angle with Kitty stands out to me as an investigator. Changing clothes and showering so quickly after a bloody knife attack is textbook evidence destruction. Blood spatter doesn’t lie, and by altering their appearance before we arrived, they tried to break the chain. Fortunately, our rapid response limited how much they could clean up. We’re still working on locating the knife itself, but the video, witness statements, clothing descriptions, and timeline provide a strong foundation.

In the interrogation room—though I can’t go into specifics on ongoing work—I approach these situations methodically. You don’t lead with the video. You build rapport. Ask open-ended questions about their relationship with the victim. How did you know Caro? What led to that day? With multiple suspects, you look for inconsistencies. One person’s story can crack open another’s. The goal is to get them narrating their version so it can be measured against the cold facts on camera.

This case has stuck with me because of its brutality in broad daylight. Knife attacks are ugly. Multiple wounds to the back and stomach speak to rage or determination. Waters mentioned he’s seen cases where personal animosity leads to dozens of stab wounds—overkill born from emotion. Here, it was contained but no less lethal. The fact that they carried it out knowing there might be cameras shows a single-minded focus that’s disturbing.

Public reaction has been intense, and I get it. The arrest video of Cookie smiling went viral for a reason. It humanizes the horror in a way that’s hard to shake. People see a mother of five gone and young women seemingly unaffected. As someone who’s stood over crime scenes and notified families, I can tell you the pain doesn’t end with an arrest.

Looking back on my participation, several things stand out. First, the efficiency of the response. From hospital to scene to arrests in hours—that’s the kind of policing that gives families answers faster. Second, the power of technology. That doorbell camera was our eyewitness. Third, the human element. Behind the headlines are children on both sides who will carry this trauma.

There’s still work to do. Indictments are pending. We’ll see what additional evidence surfaces—phone records, witness interviews, potential forensic links. The graphic images circulating online are too disturbing to dwell on, but they match what we saw in the reports.

To anyone reading this: conflicts don’t have to end in violence. A fight that starts with words or fists escalated because someone brought a knife. Now a family is shattered, three young lives are likely headed to prison, and a community is left asking why.

I’ve investigated homicides for years, but this one reminds me why the job matters. Justice for Caro Peña means holding all parties accountable under the law. Her five children deserve that much. As the case moves forward, I’ll continue doing my part—quietly, methodically, as detectives do.

If there’s one lesson from my time on this investigation, it’s that appearances deceive. The smiling suspect, the devoted mom on TikTok, the neighbor next door—none of it tells the full story until you dig into the evidence. And in this case, the evidence speaks loudly.

Stay safe out there. Conflicts have consequences, sometimes fatal ones.

Detective Brian Colwel Del Rio Police Department (Investigator on the Peña Homicide)