(CNN) -- A day after his 15-year-old son, Jordan, committed suicide by shooting himself in the chest, Brad Lewis is looking for answers.
"The suicide note he left stated that he was tired of life ... and that he was doing this because he was being bullied at school," Lewis said in a seven-minute video posted to his Facebook account on Thursday, hours after the death.
Lewis said he learned Thursday that Carterville High School in Carterville, Illinois, had shown the sophomore class a video on Wednesday about bullying. "And, at the end of the video, that the kid that was being bullied went home and committed suicide," he said.
Carterville Schools Superintendent Robert Prusator acknowledged that Jordan Lewis participated in a multimedia presentation about alcohol and drug abuse and bullying, but he said no reports had been made to the school's staff or administrators about Jordan being bullied.
"Our priority right now is counseling for our students and staff," he said in a telephone interview. "The kids are trying to get through his passing."
The elder Lewis, who works for the Illinois Department of Corrections, did not respond to interview requests. But he said in the video that he learned Thursday, as he was traveling to identify the body, that his son had told a schoolmate after the presentation on Wednesday about the bullying and about his plans to kill himself.
The girl, whom he did not identify, told her grandmother, who called police, he said. On Wednesday night, they "did a wellness check" and were supposed to have returned Thursday, he said he was told. "I never heard nothing about it until today," he said.
Williamson County Sheriff's Office Capt. Brian Thomas said police were not called to the house until Thursday, when they were contacted by the boy's mother, who had called her son earlier from her job to wake him up but got no response. She found him dead, with a shotgun wound to the chest.
The couple is separated. The boy's father lives in suburban St. Louis, about 100 miles northwest of Carterville.
Thomas said the department was investigating allegations of bullying made Thursday by the boy's relatives, but had received no such complaints beforehand.
"This bullying has to stop," the father said in his video. "People have to stop treating other people the way they do, because some people just don't have the strength to overcome the humiliation, the continuation of being picked on constantly, every day, to the point that they have no outs."
He pleaded with viewers to contact him with the names of the bulliers. "I want to find out who those kids were who bullied my son and forced him into taking his life," he said. "The only way for it to stop is to let people know what is going on so that the school can get more involved and that no other lives has to be taken."
He blamed the school video for having presented suicide as an easy out. "Just go home and take your life," he said, instead of offering counseling.
A suicide expert said that, while bullying is common, it rarely leads to suicide. "We view it as a real potential stressor for people who are already vulnerable," said Dr. Christine Moutier, medical director at the American Foundation for Suicide Prevention, in a telephone interview. "The reality is that there are other factors in there that create that level of distress and hopelessness and desperation."
Asked whether the video may have contributed to the boy's suicide, she said it was impossible to say without having seen it.
Suicide "contagion" may occur in the wake of a story that presents killing oneself as acceptable, she said.
But, she added, "We need to, as a society, not just the press, need to handle suicides in a way that's knowledgeable, that provides hope and real resources for people who are struggling, and not just a story that presents suicide as the one and only outcome."
If you are considering suicide, call the National Suicide Prevention Lifeline -- 800.273.TALK (8255).