Arapahoe High School students tearfully reunited with parents the afternoon of Dec. 13 after a lone gunman with an apparent grudge fired shots and injured two at the school before killing himself.
One 15-year-old girl remained in critical condition, one was released from the hospital and three students were treated for anxiety as crisis counselors arrived on scene after the tragedy, according to officials.
The shooter, identified as Karl Halverson Pierson, 18, was a student at the school.
Denver Archbishop Samuel J. Aquila responded to the school shooting saying, "the battle between good and evil continues."
"Unfortunately for all of us ... we are once again confronted with the effects of a culture that has little respect for life and is desperately in need of God's merciful healing," he said in a Dec. 13 statement. "As we prepare our hearts for the celebration of the birth of Christ, let's keep our youth in our prayers."
Sophomore student Tori Gilliard hugged each of her parents after being released by school authorities outside Shepherd of the Hills Lutheran Church in Centennial, a Denver suburb.
A few hours earlier she texted her parents "I love you" once she realized the school was under attack, Gilliard said.
"I just wanted to get that last word in in case something happened," Gilliard said.
Students first thought the loud noises from the hallway was a book dropping, but quickly locked the classroom doors and huddled after realizing it was a series of gunshots.
"I was just shocked at first," Gilliard said.
Dietrich and Caroline Whiteside were worried about their sons, 12th-grader Will and ninth-grader Derek when they learned of the shooting.
Will said his classroom's projector and computer started shaking after loud sounds came from the hallway.
"I didn't know what that was," he said about the noises.
Will said he and his classmates were unharmed.
Nearby, All Souls Catholic School in Englewood was locked down and parents were asked to pick up students inside. Other area Catholic schools also followed lockdown procedures.
"Our kids in the school did not know there was a shooting," said Father Bob Fisher, pastor of All Souls Church.
Reports of the school shooting began after noon Dec. 13 when emergency officials received a call about the gunfire.
Police say the suspect was armed with a shotgun and walked into the west entrance. He immediately asked students about the location of school librarian and debate coach Tracy Murphy.
"That teacher was the purpose of the suspect coming to the school," Arapahoe County Sheriff Grayson Robinson said. "There was no warning of the threat."
Murphy heard the suspect was searching for him and fled in an attempt to draw the shooter away from the school, he said.
Two students were shot in the entry of the school. The suspect then set off one of two devices police identified as Molotov cocktails, creating "a significant amount of smoke in the immediate area," he said.
The suspect then shot himself. His body was found in another area of the school, Robinson said.
News reports said Murphy had taken disciplinary action against Pierson in September. When asked about shooter's motive, Robinson said the "degree and level" of the relationship between the teacher and student was "uncertain." "I guess revenge is the word that I choose," he added.
Police searched the home of the shooter's family some hours after the shooting. Authorities stated an investigation was to continue through Dec. 16.
The shooting took place on the eve of the Sandy Hook Elementary School massacre anniversary in Connecticut and a few miles from Columbine High School, where two students killed 13 classmates and themselves in 1999. Last July was the one-year anniversary of the Aurora movie theater shooting that left 12 dead.
Archbishop Aquila said he was saddened by the tragedy and that his "heart goes out to the victims and their families."
"Let us pray that as a culture we find the path to peace and to goodness that begins with accepting God's mercy and forgiveness, and his eternal love for each and every human being," he said.