By Eliott C. McLaughlin, CNN

(CNN) -- The father of the teenager accused of killing 10 people at Santa Fe High School in Texas says his son was a "good boy," and he believes bullying drove him to perpetrate last week's deadly rampage.

Antonios Pagourtzis' claims came during a brief phone interview Monday with The Wall Street Journal.

Pagourtzis' son, 17-year-old Dimitrios Pagourtzis, is on suicide watch at the Galveston County Jail, where he is being held without bail. He has not entered a plea to the charges of capital murder of multiple people and aggravated assault on a public servant.

In a probable cause statement, authorities said he admitted to the shooting.

His father told the Journal that Dimitrios was "mistreated at school" and "I believe that's what was behind" the shooting.

In a statement over the weekend, the Santa Fe Independent School District said it was aware of false reports "about SFISD high school coaches and bully-like behaviors toward the student shooter." The administration investigated the claims and determined they were untrue, the statement said.

Father had run-ins with law

Pagourtzis, who business records show owns North American Marine Inc., a ship repair and industrial cleaning company in Houston, north of Santa Fe, told the Journal he struggled to get where he is today. He left his village in northern Greece when he was 12 with only the clothes he was wearing and a spare set of boots, he said.

"This country treated us well. I worked hard and became a shipowner. I had three ships, which I sold," he told the paper. "Now ... our lives are shattered."

According to Harris County, Texas, court records, Pagourtzis was twice charged with misdemeanor assault -- in 1987 and 2012 -- and both cases were dismissed. In 2008, he was convicted of illegally dumping wood materials, records show.

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In the 2012 case, Pagourtzis punched a man and "grabbed his face and hit his head on the ground causing his nose to bleed" after, Pagourtzis alleged, the man hurt dogs at his shop, a police affidavit said.

It's unclear why the cases were dismissed, and neither Pagourtzis' nor the alleged victim's attorneys could be reached for comment.

Approached at the rusting North American Marine warehouse, Dimitrios' half-sister, Katina Pagourtzis, declined to comment on her father or Dimitrios.

The guns

During the interview with The Wall Street Journal, Antonios Pagourtzis wouldn't discuss how his son came to acquire the weapons used in Friday's attack, the paper reported.

The suspect was armed with a sawed-off shotgun and a .38-caliber handgun, and Texas Gov. Greg Abbott said last week that the teen obtained the guns from his father, but a law enforcement official told CNN that authorities are still trying to determine whether that's the case.

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Sawed-off shotguns are illegal without a permit from the Bureau of Alcohol, Tobacco, Firearms and Explosives. The .38-caliber handgun was purchased in the early 1990s, the official said.

Investigators have identified the original buyers, but how Dimitrios ultimately obtained the weapons is still under investigation, the official said.

In a Saturday interview with Greece's Antenna TV, Pagourtzis said he owned the guns used in the attack and Dimitrios took them from his closet.

Dimitrios worked out and didn't drink or get into fights, he told the station. He said he ate and played with his son the night before the shooting, and Dimitrios left early the next morning. When the father asked why he was leaving early, Dimitrios replied, "I'm off, I love you and I'll see you in the afternoon," Pagourtzis told Antenna.

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"I feel the pain of the others, but I have the same pain. I have the same exact pain," Pagourtzis said, according to a translation of the interview. "Something must have happened now, this last week. Somebody probably came and hurt him, and since he was a solid boy, I don't know what could have happened. I can't say what happened. All I can say is what I suspect as a father, because I've lost my boy.

"My son, to me, is not a criminal. He's a victim."

Suspect won't face death penalty if convicted

Two school resource officers arrived at the school about four minutes after the shooting started and engaged Dimitrios, enabling other officers to evacuate teachers, administrators and students, Galveston County Sheriff Henry Trochesset said.

Officers exchanged gunfire with Dimitrios before a 25-minute negotiation ended in his surrender. The suspect and officers did not exchange gunfire during the negotiation, the sheriff said.

"From what I see, I don't believe any of the individuals that were killed" were shot by law enforcement during the crossfire with the suspect, Trochesset said, adding he can't be 100% certain until the autopsies are complete.

The cause of death for each victim was gunshot wounds, according to John Florence, chief investigator for the Galveston County Medical Examiner's Office. It's unclear when the autopsies will be complete, Florence said, and release of the completed autopsies could be delayed at the prosecutor's request.

Dimitrios told an investigator he acted alone and spared people he liked because he wanted his story told, according to a probable cause affidavit.

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The massacre claimed the lives of students Sabika Sheikh, Shana Fisher, Jared Black, Chris Stone, Angelique Ramirez, Christian Riley Garcia, Aaron Kyle McLeod and Kimberly Vaughan. Teachers Glenda Ann Perkins and Cynthia Tisdale were also killed.

Houston police Officer John Barnes, a resource officer at the school who confronted the gunman, was among the victims hospitalized.

Barnes was in intensive care following surgery Monday, said Walter Braun, police chief of the Santa Fe Independent School District.

The suspect won't face the death penalty if he is convicted. Under Texas law, offenders younger than 18 who are charged with a capital offense face a maximum penalty of life in prison with the possibility of parole after 40 years.

The governor on Tuesday afternoon will host the first of three roundtable discussions to address school security. The roundtable will include school administrators, politicians, law enforcement officials and an architect with expertise on school design, among others, according to the governor's office.

On Wednesday, district teachers and support staff will return to school, the district said. All students will return Ma 29, the district said.