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LENEXA, Kan. — An off-duty officer happened to be in the right place at the right time: the Costco on Marshall Drive in Lenexa around 11 a.m. Sunday.

Ryan Vacca said he was working at the Costco photo center when, “I was looking at the computer screen, and then I heard some commotion happening around me.”

Then, “I turned and looked at the front door and saw a guy walking in – just kind of yelling and screaming.” Vacca continued, “one of my co-workers told me to drop, and I did.”

Captain Wade Borchers of Lenexa police confirmed that a man walked into the store just after 11 a.m. Sunday morning, brandishing a firearm.

Moments later, terror drove the Costco crowds to the exits.

Except for one man. Among the many shoppers at the Lenexa Costco this major shopping weekend was an off-duty Kansas city, Kan. officer.

“He was just shopping,” said Capt. Borchers. “He was just shopping, and he happened to be there while all this occurred. And you know, thankfully, he was.”

But despite the masses of panicked people packed in the parking lot, there were still some inside. Nikki Lotia was one of them.

“I saw the crowd running, and it said ‘run at the back, run at the back!’ So I started running,” she said. “Instead of running with the crowd towards the back, I went towards the pharmacy area.”

All she could do was look for a place to hide.

“I just grabbed two chairs and I just went into the corner.”

“My phone says I called 911 around 11:11. And I could hear the guy (on the phone) asking, ‘what’s your emergency?’ And I was so scared and shaking. I didn’t want to say anything loud, so I just kind of whispered, ‘shooting, you know, Costco.'”

Then, Lotia sent a text message to her son.

Ali said, “around 11:15, she texted me that there’s a shooting going on and I’m hiding.” So I freaked out.”

Ali showed FOX 4 the text messages she sent while hiding in the store. For every three Ali received, she sent one; worried any sound would attract attention.

“And soon, I heard four shots, you know? Like, I heard, duh-duh-duh-duh-duh. And I thought, ‘oh my God.’ And I just kept there, and started praying.”

She made it home safely, though for a time, she thought she wouldn’t.

“It was very scary,” she said. “That 45 minutes of my life. All of the time I was thinking, ‘this might be my last day.'”

This Thanksgiving weekend, she is very grateful to be home with her family, and for that unnamed off-duty officer shopping at Costco.

“He was there right in time,” she said, “and he saved everyone, and he saved my life. I’m thankful for him.”