Carrying her 11-month-old daughter, she quickly searched for safety.
"I just remember running and clutching her as tightly as I could," Johnson said. "I was thinking 'God help us get out of here. Help her to see her first birthday, which is in two more days'."
Johnson was volunteering in a booth, along with three other women, for the first time this year during the three-day annual festival that saw more than 100,000 guests come through their doors.
The Garlic Festival is something she looks forward to every year.
"It's very family-friendly," Johnson said. "You feel safe, then something like this happens."
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At first, Johnson thought the loud "pops" that she heard was fireworks going off.
It was not fireworks.
Santino William Legan, 19, opened fire on crowds injuring more than a dozen people.
Three of those people died from their injuries.
RELATED: What we know about the 3 killed in the Garlic Festival shooting
When she witnessed what was happening around her, she quickly knew she had to spring into action to save herself and her child.
"We saw this huge swarm of people running and screaming, 'there's someone shooting, run, run'. We just picked up my baby and ran to the back of our little trailer thing and closed the door."
PHOTOS: Aftermath of shooting at Gilroy Garlic Festival
After several minutes, Johnson was escorted out of the trailer by police to another holding area.
She was not able to leave the property for more than three hours, holding onto her baby the entire time.
While she says the police and festival employees did a great job with the aftermath, she thinks there could have been more done in advance of the tragedy.
Hannah Johnson survived the #gilroygarlicfestivalshooting by clutching her 11-month-old in a trailer behind a booth. She said security was a concern of hers before the shooting occurred on Sunday. Hear her story of survival tonight on ABC7 News at 11pm. https://t.co/nEsDhMV7Vg pic.twitter.com/r0AIuorRt4— Dustin Dorsey (@DustinABC7) July 30, 2019
"One thing that kind of stood out to me, or shocked me, was that as we were going in and you're a vendor and you show your pass for that, they don't look through your bags," Johnson said. "Someone that is smart and wanting to do harm would think that is the perfect get through."
While the suspected gunman was said to have come onto the property through the Uvas Creek, she still believes the security could have been better given other mass shootings that have happened in the country.
We took a walk and a drive from #SantinoWilliamLegan’s home on Churchill Place to see how long it would take to get to the Uvas Creek where he reportedly made his way into the #GilroyGarlicFestival. It turns out it takes less than 2 minutes to arrive. https://t.co/WY51zKFGBn pic.twitter.com/Oi2hXUQ41y— Dustin Dorsey (@DustinABC7) July 29, 2019
When all is said and done, Johnson is thankful to be alive.
She adds that she still sees the horrific scenes in her head and can hear the "pops" of the gun going off.
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But she still knows that things could have been much worse.
"My family was supposed to be there. My husband was going to bring my girls, I have four of them. If that would have happened, and he's alone with all four, there would've been a different end to this story. We wouldn't be all home safe like we are."
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