A boy secretly videotaped his father beating the child’s 2-year-old disabled brother and then reported it to authorities at his middle school in Texas, police said.

The sixth-grader told officials at his Leander school about the alleged abuse — including beatings with a belt and a fly swatter — prompting an alert to the Williamson County Sheriff’s Office last week, according to an arrest affidavit obtained by the Austin American-Statesman.

The boy reported that he saw his 48-year-old father, Alejandro Gonzalez, grab his younger son by the hair during an incident on May 22 — violently shaking the toddler while he was sitting in a high chair at their home about 30 miles north of Austin.

Gonzalez, according to the affidavit, became angry that that boy, who has difficulty chewing and swallowing due to cerebral palsy, would not eat.

The older brother used his cellphone to record Gonzalez violently shaking the toddler and then sent the footage to his older sister to prevent his father from finding it on his phone.

A deputy who watched the disturbing clip said it confirmed what the boy had told him about the abuse. The deputy was also shown photos of bruises and red marks on the victim’s buttocks and lower back, according to the affidavit.

Those marks were caused by Gonzalez “disciplining the child using a belt and a fly swatter” on another occasion, the affidavit reads.

Gonzalez was charged with injury to a child, a third-degree felony. If convicted, he faces up to 10 years in prison. He remains jailed on $100,0000 bail, the American-Statesman reports.