The teen who has admitted to killing four people and injuring seven others during a shooting rampage in La Loche told his caseworker at a youth facility he became "obsessed" and "messed up" from watching mass shooting videos online.

The teen's primary caseworker at Kilburn Hall, Christopher Hales, testified Wednesday during a hearing to decide if the teen should be sentenced as an adult.

The shooter's identity is protected under the Youth Criminal Justice Act. He was weeks away from his 18th birthday when, in January 2016, he killed two brothers at a home in La Loche before fatally shooting a teacher and an aide and injuring seven other people at the La Loche Community School.

Hales told court he asked the teen, during a half-hour conversation at Kilburn Hall, why he opened fire at the school.

The teen said he just wanted to know when it felt like and said he got "an extreme scary rush after pulling the trigger,” according to Hales.

The caseworker also said the teen told him, "Everyone wants to know why. Everyone is constantly asking me why. Why did I do this?"

Hales said the teen has been the subject of seven incident reports since entering Kilburn Hall in Saskatoon. Four of the seven reports were about concerns of self-harm, according to Hales.

In a March 2017 incident, Hales said the shooter was having an "off" night and was upset about killing the two brothers. The teen slipped a note under his door, which read "F--- life" and showed a stick figure holding a gun to its head.

He chose to be placed in a holding cell, where he was checked on every five minutes. During that time, he was seen giving the middle finger to a security camera and firing a fake gun at it, according to Hales.

He testified the teen had told him he wishes he shot himself when he had the chance.

Hales also said the shooter "tends to glorify violence" and that he's had to speak with the shooter about his attitude toward violence, including when he makes jokes about joining ISIS or makes light of other violent incidents seen on television.

At the beginning of June, the teen was moved up a security level at Kilburn Hall and was heard bragging to other residents about how dangerous he is. He also said he's in jail because it's fun, and he portrayed himself as famous because the shooting has been on the news, Hales testified.

There are reports made by Kilburn Hall staff of the teen swearing at staff, punching walls, throwing items in his room and disrespecting staff, but in many of those cases the behaviour wasn't severe enough to result in an incident report, Hales said.

Hales said under cross-examination the teen still has progress to make, but said the shooter has made significant behavioral and educational improvements during his time at the facility.

The Crown closed its case Wednesday and said it believes the teen should be sentenced as an adult.

“In particular given his advanced age for a young person and the extreme seriousness of the offences, and the extremely serious and grave impact that it had on the community and the victims,” Crown prosecutor Lloyd Stang told reporters outside court.

The shooter pleaded guilty to two counts of first-degree murder, two counts of second-degree murder and seven counts of attempted murder in October 2016.

In the days leading up to the shooting, and on the day of, the teen searched subjects on the Internet about guns, school shootings and what it feels like to kill, according to an agreed statement of facts in the case.

On January 22, 2016, the teen shot and killed brothers Dayne and Drayden Fontaine in a home in La Loche. Dayne was shot 11 times after pleading for his life, according to the agreed facts. The shooter later expressed remorse for killing the brothers, saying it wasn’t part of the plan, but going to the school and opening fire was.

While driving a truck to La Loche Community School the shooter posted in a Facebook group chat, writing, “just killed 2 ppl” and “bout to shoot ip (sic) the school.”

Inside, he opened fire and killed teacher Adam Wood, 35, at close range and teacher’s assistant Marie Janvier, 21, through a classroom window. He injured seven others.

RCMP officers arrested the teen after he exited a school washroom unarmed, announcing he was the shooter. He entered the school at 1:04 p.m. and was arrested at 1:16 p.m., according to the agreed facts.

Many of the 46 people who filed victim impact statements with the court, including those who were injured in the shooting and family members of those who were killed, read them aloud during the first portion of the hearing in May. Many explained their symptoms of post-traumatic stress disorder and some asked Judge Janet McIvor to sentence the teen as an adult.

On Wednesday, McIvor granted a request the defence filed two weeks ago to order a Gladue report, which looks at circumstances of indigenous offenders when determining a sentence.

“As some of the facts have come out it’s pretty clear there's some history there that we think is relevant,” defence lawyer Aaron Fox said outside court. “This is just too serious a matter not to have that covered off. So we think we can get the report done in fairly timely fashion.”

The defence will begin presenting evidence Thursday and is expected to call a psychiatrist and family witness. A psychologist is scheduled to testify Friday and Fox said the shooter himself will likely make a statement that day.

No dates have been set for closing arguments in the case.

--- CTV is in Meadow Lake for the sentencing hearing. Follow our coverage: