A teenage cousin of the shooter responsible for the Uvalde school massacre has been arrested after threatening to shoot up a local primary school.

The boy’s mother reported his plans to police after he was planning to “do the same thing” as his cousin, Salvador Ramos, the Daily Mail reported.

Ramos was responsible for killing 19 students and two teachers at Robb Elementary in 2022.

Gunman Salvador Ramos. Photo / AP

Nathan Cruz, 17, told his sister what he was planning to do, and she then told their mother what his intentions were.

Documents reveal the family live close to a primary school.

A memorial honouring the school shooting victims at Robb Elementary in Uvalde, Texas. Photo / AP

According to Cruz’s mother, he was intoxicated when he made the violent threats and is currently on probation.

Cruz was immediately arrested and sent to Bexar County Jail on a felony charge of making a terroristic threat to the public.

He has also been charged with making a terroristic threat to a family member.

According to his warrant, one of Cruz’s family members told police she heard him talking to an unidentified person on the phone where he wanted to “acquire an AR-15 through an illegal private sale”, the Daily Mail said.

Report finds ‘systemic failures’ in Uvalde school massacre

A damning report last year prompted questions over the bewildering inaction by heavily armed officers as the gunman fired inside a fourth-grade classroom at Robb Elementary.

Nearly 400 law enforcement officials rushed to the school but “systemic failures” created a chaotic scene that lasted more than an hour before the gunman who took 21 lives was finally confronted and killed, according to the report.

The nearly 80-page report was the first to criticise both state and federal law enforcement, and not just local authorities in the South Texas town for the inaction.

Altogether, the report and more than three hours of newly released body camera footage from the May 24 tragedy amounted to the fullest account to date of one of the worst school shootings in US history.

Some families blasted police as cowards and demanded resignations.

- Additional reporting, AP