(UVALDE, Texas) -- A young teen who allegedly exchanged private messages with accused Texas gunman Salvador Ramos in the weeks leading up to Tuesday's attack on Robb Elementary School told ABC News that she has been asking herself, "What if I could change the outcome?" after authorities said Ramos killed 19 students and two teachers at the school.
"Ever since May 24, I have been guilt-tripping myself: What if I could change the outcome? What if I could change his mind to not do this?" said the teen, who asked to be referred to as "Cece."
"I was too dumb to realize why he bought two rifles on his birthday, May 16, and ordered a package full with ammunitions, not knowing what he was going to do with it," she said.
Law enforcement sources tell ABC News that the private messages are part of the ongoing investigation into the shooting.
Cece, who lives in Germany, said she met Ramos on the social media app Yubo, where they would "join each other's live" streams. The pair met only a few weeks ago, in early May.
On the morning of the shooting, Ramos allegedly messaged Cece to describe an argument he was having with his grandmother over a phone bill, before texting, "I shot my grandmother in the head" and "ima go shoot up a elementary school rn."
In a previous interview with The New York Times, Cece said she read Ramos' messages "as soon as he sent them," which would have been minutes before the shooting. However she told ABC News that she "misspoke" and that she only saw the messages "hours later."
The messages, which were reviewed by ABC News and other media outlets, appear to show that Cece did not respond to the gunman's threats until after news of the shooting broke. Nearly all the texts are solely from Ramos, although it's unclear if the messages were at all edited.
Cece said she met Ramos around May 9 on Yubo -- a social media app that has been described as a dating app for teens -- when they were both in "random" live streams together. They subsequently began talking regularly and also exchanged cell phone numbers, Cece told ABC News.
She said that after Tuesday's attack, she heard rumors from her friends that Ramos could be the shooter -- but she didn't believe them.
Then, after seeing news of the shooting, Cece says "the puzzles started to fit" together, and she reached out to a friend who lived in the United States to help contact law enforcement.
The young teen claims that, in hindsight, there were other warning signs. Prior to the shooting, she said, Ramos asked others on Yubo if they would wanted to be famous on the news.