Throughout her freshman and sophomore years at Columbine High School, Jenica Thornby went to the library every single day.

“Not one day went by that I did not go to the library,” Thornby recently told “EWTN News In Depth” reporter Catherine Hadro. “Except one day.”

That day was April 20, 1999. 

“I was 16 years old, and I was sitting in my art class when all of a sudden I had this overwhelming urge to leave school,” she recalled. “I just over [and over] in my head kept repeating, ‘There’s no way I’m staying here. There’s no way that anyone’s going to talk me into staying.’”

Thornby convinced a friend to leave campus with her — they could go study at a local restaurant instead, she told her friend — and the two left school in Thornby’s new car that she had just driven to school for the first time that day.

“The moment we turned on the car and started to leave the parking lot and drive away, I looked in my rearview mirror and noticed hundreds and hundreds of schoolmates of mine just running out of the school, and we had no idea what had happened,” she recalled. “We thought maybe it was a fire drill, but we didn’t understand.”

Principal Frank DeAngelis, a lifelong Catholic, vividly remembers his secretary coming into his office that day to tell him about reports of a shooting.

“All of a sudden I come out of my office, and my worst nightmare becomes a reality because I encounter a gunman coming towards me,” he told Hadro.

DeAngelis said he started praying in his head and everything slowed down. He sprinted toward the gunman, managing to avoid gunshots. He then focused on getting as many students as possible into the gym and out of the building.

“I pull on the gymnasium door, and it’s locked. And all of a sudden, we hear the sounds of the shots getting closer,” he recalled. “The gunman’s coming around, and I had 30 keys on a key ring. I reached in my suit pocket, stuck the first key that came into my hand, and it opened [the door] on the first try, or I would not be having this conversation [right now].”

It was 25 years ago that two gunmen killed 12 students and one teacher before turning their guns on themselves at Columbine High School in Littleton, Colorado, a Denver suburb. The massacre was the deadliest K-12 shooting in U.S. history at the time, only to be surpassed by the Sandy Hook tragedy in 2012. 

“Reflecting back, I knew that was something beyond me,” Thornby, now Sister Mary Gianna, told “EWTN News In Depth.” After leaving campus in her car that day, as the events unfolded, she learned that 10 of the 12 students killed were in the library. She overheard an adult say that God must have a plan for her life.

“I had this urge to leave. God has a plan for my life, and so I did bring that to God after I found faith,” she said. “You know, ‘Why did you allow me to survive?’”

A year after the shootings, a friend invited Thornby, who grew up without any faith, to the local Catholic church. When she was 18, she was invited to Eucharistic adoration. She eventually attended Franciscan University of Steubenville, Ohio, and was received into the Catholic Church when she was 19 years old, on March 30, 2002. 

After college she did missionary work and one day, she picked up a book by Father Benedict Groeschel.

“He said, ‘Instead of asking God why something happened, ask God, what would you have me do?’ And so instead of reflecting on my life, why did this happen? … Why did the shootings happen? I started to pray and ask God, okay, what would you have me do?”

(Story continues below)

Eventually Thornby discerned life as a religious sister and is now a member of the Disciples of the Lord Jesus Christ in Prayer Town, Texas. 

DeAngelis said he had his first crisis of faith the night of the shootings. But not long afterward, a priest friend called him to the church and shared some spiritual insight.

“He said, Frank, you should have died that day, but God’s got a plan,” he recalled. “And he quoted Proverbs 16:9. He said, ‘In his heart a man plans his course, but the Lord determines his steps.’ And he said, you’re going to have to go rebuild this community and help others.”

Watch the full “EWTN News In Depth” interview with Thornby and DeAngelis below.