Maisch was waiting on line to meet Rep. Gabrielle Giffords and was about 20 feet away from the congresswoman when gunfire erupted without warning.
"The only warning was the first shot," Maisch told "Early Show" anchor Erica Hill on Monday.
Special Section: Tragedy in Tucson
"I heard a shot and I just knew that it was gunshot," Maisch said. "There was one shot and then a series of shots.
"So I had to make a split-second decision whether I was going to run, or I was going to drop to the ground," she continued. "And I thought if I ran, I might become a target. So I dropped to the ground.
"He shot the woman that was next to me, and I was just waiting for the next bullet," Maisch said.
Then Maisch saw the gunman was on the ground near her. "Two gentlemen had knocked him to the ground, and somebody yelled 'Get the gun,'" Maisch said. "So I knelt up - he was on his right side - I knelt up and reached over him. I couldn't reach the gun, but as he was doing that he also pulled another magazine out of his left pocket, which he dropped on the pavement, and I was able to get it before he did.
"At the same time, another gentleman had picked up the gun. So he was secured."
She said she could not get a good look at the gunman's face. "He had a stocking cap on, and the way he was pushed on the ground, I could only see a little bit of the left side of his face, 'cause he had the stocking cap almost up to his eyes, both at the side, and above his eyebrows," she said.
"And I was on his legs when - after I got the clip, he was struggling, and kicking his legs, so I knelt on his legs. And then I noticed that the one gentleman, Bill, who had knocked him down had a head wound, so I asked somebody else to come and take my place and ran into Safeway and got some towels, and made a compress for Bill's head."
"A lot of quick thinking on your part and so many others," said Hill.
"I think it's pure adrenaline," Maisch said.
She rejected praise that her actions were heroic, saying the two men who tackled the suspect are her heroes. "I was not one of the heroes; the two that knocked him down had the courage to do that, [they] are the heroes."
She said it was difficult to ponder the events of that day: "It's hard for me to think about the people that died on the sidewalk, and how long their bodies had to lay there, and the little 9-year-old girl," Maisch said. "It was so senseless to take out innocent people. It's a shame that there's so much hate, political."