A woman in Texas was shot and killed in a PetSmart parking lot after an argument over not saying “thank you” for opening the door, according to police.

Cecilia Simpson, 41, was shot several times outside a PetSmart in Dallas on Tuesday at around 1 p.m., Dallas police told FOX 4. A witness told police that Simpson held the door open for Keona Zachyua Hampton, 22, at a Five Below store, an arrest affidavit states.

Simpson allegedly became irritated that Hampton didn’t thank her for holding the door open, triggering an argument. Simpson and her daughter went to their car and drove to PetSmart, which was in the same plaza.

When Simpson and her daughter entered the PetSmart store, she told employees they were being followed by Hampton. Hampton allegedly walked into the store and began arguing with Simpson’s daughter. Hampton exited the store, but returned a few minutes later, when she allegedly started another argument with Simpson.

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After being asked to leave the store, Hampton allegedly threw a bottle at the vehicle Simpson was driving with her daughter in it. According to police, a physical fight then ensued when Hampton took out a handgun and allegedly shot Simpson three times.

Hampton was arrested on Tuesday night during a traffic stop and admitted she got into an argument with Simpson, but claimed she only took out the gun when the situation became physical.

Hampton was booked into jail on a murder charge. Her bail hasn’t been set.

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An ER nurse who saw the incident told FOX 4 her perspective on what happened.

“The shooter was saying, ‘Come outside. Let’s handle this outside. Let’s fight outside.’ And the mom and daughter were just telling her to like go away,” she said. “The mother and daughter tried to get in the car to de-escalate the situation but the lady wasn’t having it. They started to fight and that’s when the lady pulled out her gun and shot her.”

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The nurse said she performed CPR before paramedics arrived.

“The daughter was next to the mom the whole time. It’s hard, you know, because the screaming of a child for her mother is never easy and it’s never going to leave my head,” she said. “I’ve been trying not to cry, but just like, you know, being in high school, my mom was such an important person in my life and she’s the reason I became a nurse. My whole family is.”