Story highlights Grandfather credits Cassidy Stay with saving 20 lives by alerting authorities

He says she played dead after being shot, then told police others were in danger

The teenager speaks out for the first time, after her parents and 4 siblings were killed

Cassidy quotes from Harry Potter: "Happiness can be found even in the darkest of times"

Cassidy Stay has seen the worst -- the brutal killings of her parents and siblings, ages 4 to 13, in their Texas home.

On Saturday, the 15-year-old quoted Dumbledore, the wise man from the Harry Potter series, in hopes of finding some good amid the horror.

"Happiness can be found even in the darkest of times," Cassidy said, citing J.K. Rowling's "Harry Potter and the Prisoner of Azkaban," "if one only remembers to turn on the light."

The remarks -- at a public memorial for her family -- were the teenager's first public comments since she emerged as the lone survivor from the carnage in her family's Spring home.

Authorities say that Ronald Lee Haskell barged into residence on Wednesday demanding to know the whereabouts of his estranged wife.

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She was not there, but the Stay family was. And soon, in a barrage of bullets, six of them were dead.

They included Cassidy Stay's parents, Stephen and Katie, as well as her 7- and 9-year-old sisters and 4- and 13-year-old brothers.

Cassidy was targeted as well, with the Harris County Sheriff's Office indicating the shooting left her in critical condition. By Saturday, though, she was not only out of the hospital but standing tall, wiping away tears as people remembered her parents and siblings and offered support to her.

Thanking the first responders, doctors and nurses who'd helped her, the teenager said, "I am feeling a lot better and am on a very straightforward path to a full recovery."

Unfortunately, her family isn't coming back.

Reminders of this were everywhere, including a board that had hearts with their names. Cassidy mentioned them too, right after quoting Dumbledore.

"I know that my Mom, Dad, Brian, Emily, Becca and Zach are in a much better place, and that I will be able to see them again one day," she said at the gathering.

Grandfather: Cassidy saved 20 lives

At the same ceremony outside Lemm Elementary School in Spring, Roger Lyon remembered his daughter Katie, his son-in-law and grandchildren, saying, "We will miss them in the morning and in the evening."

"The best way, we think, (to move on) is to concentrate on the living, to cling to hope of life that has emerged in this terrible darkness."

He was talking about Cassidy.

Lyon then recounted what the teenager had done -- how she'd been shot and how she'd seen her parents and siblings shot. After all that, her grandfather said Cassidy "had the presence of mind to remain quiet and to play dead."

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Once the coast was clear, the teen got up, called police "and told them we were in danger."

"Without her courage and quick thinking, we might be mourning the deaths of 20 -- yes, I said 20 -- people today, including myself and nearly all of our children and grandchildren," Lyon added, crediting Cassidy for alerting authorities who headed off Ronald Lee Haskell and arrested him after a three-hour long standoff.

While in the hospital, Cassidy talked about angels she'd learned in Sunday school are sent to "protect his children in times of great need," according to Lyon.

"After she had been shot on Wednesday, she said it felt as though the angels were there with her, putting their hands over her mouth -- whispering to her to be quiet," her grandfather said. "'I was quiet when I needed to be quiet,' she told us."

Between the balloons being released into the sky in the Stay family's memory, in between all of the tears and the hugs among those in the crowd who knew them, there were many reminders of Cassidy's actions -- and not just from her grandfather -- on Saturday.

Her name, after all, was among those on the board with those of her slain family members.

Hers was the only heart that wasn't red. And it was the only one with extra words added: "Our hero."