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.