The teenage student who killed 10 people when he opened fire on the art class in his Houston-area high school appeared “weirdly non-emotional” on the morning after the rampage, one of his lawyers says.

The appraisal of Pagourtzis’ inert mental condition comes on the heels of investigators revealing the shooter deliberately spared his friends during the bloody rampage.

The accused killer, 17-year-old Dimitrios Pagourtzis, has been charged with capital murder and is being held without bail in Santa Fe, Texas, where he went on the shooting spree on Friday.

According to preliminary law-enforcement documents listing charges against Pagourtzis and made available to the press, he wanted favoured survivors to tell his side of the story.

Pagourtzis had intended to commit suicide, according to investigators, but lost his nerve after a shoot-out with a school guard.

In addition to 10 fatalities, the gunman wounded at least 13 people, with two of them still listed in critical condition. One of those with the worst wounds is the hero school resource officers who exchanged fire with the shooter before his surrender.

Nicholas Poehl, one of two lawyers hired by the suspect’s parents to represent him, told Reuters he had spent a total of one hour with Pagourtzis on Friday night and Saturday morning.

“He’s very emotional and weirdly non-emotional,” the lawyer said when asked to describe his client’s state of mind.

“There are aspects of it he understands and there are aspects he doesn’t understand.”

Pagourtzis’ family said in a statement they were “saddened and dismayed”  and “as shocked as anyone else” by the events. They said they are co-operating with authorities.

Investigators had seen a photo of a T-shirt on the suspect’s Facebook page that read “Born to Kill,” and authorities were examining his journal, Texas Governor Greg Abbott told reporters. But there were no outward signs he had been planning an attack.

Pagourtzis waived his right to remain silent and made a statement to authorities admitting to the shooting, according to an affidavit.

Asked if Pagourtzis had provided authorities with information about the shootings, Poehl said: “Honestly because of his emotional state, I don’t have a lot on that.”

Santa Fe High School, southeast of Houston, became the scene of the fourth-deadliest mass shooting at a US public school in modern history, joining a long list of campuses where students and faculty have fallen victim to gunfire.

-with AAP