(Photo: Courtesy of Arapahoe County Sheriff')
The parents of the student gunman who critically wounded a classmate at Arapahoe High School on Friday say they’re praying for his victim. Barbara and Mark Pierson released the following statement this afternoon:

"We are shattered by the tragic events that took place on Friday at Arapahoe High School. Our thoughts and prayers are with Claire Davis and her family. They, and she, have suffered unimaginably, and we pray for her full recovery. We also pray for the entire Arapahoe High School community, as we know your lives are forever changed by this horrific event.

As parents, we loved our son Karl dearly and we are devastated by what happened Friday. We cannot begin to understand why Karl did what he did. We ask for privacy during this unthinkably difficult time and hope that you will respect our need for time to grieve."

About 500 people gathered Sunday night for a candlelight vigil to show support for 17-year-old Claire Davis, who remains in critical condition at Littleton Adventist Hospital.

Davis was wounded on Friday by Karl Pierson just before the 18-year-old gunman took his own life at Arapahoe High School.

Arapahoe County Sheriff Grayson Robinson told reporters over the weekend they believe that Pierson sought revenge against a faculty member as a motive for the shooting.

Sheriff Grayson Robinson said in a statement on Monday that investigators finished their work over the weekend gathering evidence and is allowing school district administrators back into the Arapahoe High School facility.

Robinson on Saturday released a statement from Davis’ family concerning the condition of their daughter.

"Our beautiful daughter Claire Davis has severe head trauma as the result of a gunshot wound,” the family said in a statement. “She needs your continued prayers.”

Sheriff Robinson said that Pierson entered the school intending to hurt many people and that the incident took 1 minute and 20 seconds, from the time he entered the school to the time Pierson took his own life. 

"The gunman [Pierson] entered the school with a pump shotgun with multiple rounds and the intention to use them to hurt people," Robinson said on Saturday.

Robinson said video surveillance showed Pierson carrying a pump-action shotgun, a bandolier full of ammunition and a backpack that was later discovered to include three incendiary devices resembling a Molotov cocktail.

The shotgun, according to Sheriff Robinson, was purchased legally on Dec. 6 at local retail outlet by the 18-year-old gunman but the ammo was purchased prior to arriving at the school on Friday morning.

Robinson also confirmed that one of the devices was lit and burned in the school library where Pierson committed suicide just before deputies could apprehend him. 

Gov. John Hickenlooper said during a Sunday appearance on CBS’s Face the Nation program that Pierson displayed no warning signs about his intentions.

"He [Pierson] didn’t seem to have a mental illness," Hickenlooper said. “There’s nothing that says, 'ah, now I understand'."

At 12:33 p.m. on Friday, a police officer stationed at Arapahoe High School reported a gunman on campus carrying a shotgun and looking for a particular teacher.

“Our initial investigation is causing us to believe that this shooting is the result of revenge on the part of the shooter, because of a confrontation or a disagreement between the shooter and the teacher,” Arapahoe County Sheriff Grayson Robinson said during an afternoon press conference. 

The teacher, who officials are not naming at this time, got wind that a gunman was looking for him and left campus immediately.  Sheriff Robinson said that action by the teacher probably saved lives.

“He knew he was the target and he left that school in an effort to try to encourage the shooter to also leave the school with the focus of safety and security and well-being of our students in his mind,” Robinson said.

A short time after the initial shots, Sheriff Robinson said deputies found the assailant in a classroom with a self-inflicted gunshot wound.

Robinson praised the fast response times, noting officers trained for a scenario like this recently.

“Those protocols, unfortunately, have had to be used far, far, far too many times in Colorado and across the United States because of these tragic episodes where people decide they have got to even up the score with a weapon,” Sheriff Robinson said.

The shooter was also armed with two Molotov cocktails, one of which was detonated during the attack, causing a small fire.

Deputies on the scene reported encountering a cloud of smoke in the school but there were no reports of injuries from the fire.

At an evacuation point across the street from the high school, teary-eyed parents hugged sons and daughters.

Arapahoe High sophomore Sofia May said there was confusion after the first gunshots rattled her class. 

“At first I thought maybe someone dropped a book or something like that,” May said.  “People were looking around and I realized it was gun shots -- we thought it was a drill at first, but obviously not.”

Her mom, Denise Andert, looked extremely relieved as she reunited with her daughter.  

Andert echoed many parents and kids here in her disbelief that this could happen to them.

“You always see it on TV,” Andert said. “You always like assume it’s going to happen to everybody else, or just not happen again. It’s insane.”

Andert and her daughter live in this neighborhood by the school, which is less than 10 miles from Columbine High School, the scene of a horrific mass shooting 14 years ago.

Megan Verlee, Pat Mack and Ben Marcus contributed to this report.