Flowers are piled around crosses with the names of the victims killed in a school shooting as people visit a memorial at Robb Elementary School to pay their respects May 31, 2022, in Uvalde, Texas. AP Photo/Jae C. Hong, File

A cousin of the Uvalde gunman has been arrested after allegedly threatening to shoot up a local school just over a year after his relative fatally shot 19 students and two teachers at Robb Elementary School.

He was planning to “do the same thing” as his cousin, the teen’s mother said, according to the affidavit in his arrest, and tried to purchase an AR-15 rifle on Monday. The 17-year-old, whom The Washington Post is not publicly identifying because he has not been charged as an adult, also threatened to shoot his sister in the head and told her he would “shoot the school,” according to the affidavit.

The suspect’s mother called police Monday after hearing from her daughter that her son had made the threats. The teen allegedly was riding in the car with his sister when he threatened to shoot her and attack the school, also saying, “School is starting soon,” the sister reported to police.

The teen denied making the threats, according to the affidavit. It was not immediately clear whether he had a lawyer.

His mother told police she was especially concerned because the family lives across the street from an elementary school, the affidavit said, and because the teen was intoxicated when he said it and is on probation. His sister “feared the suspect would act on his threat to shoot her” and “believed that the threat to the school was credible due to the recent history of his family and the suspect’s knowledge of his cousin’s actions,” a San Antonio Police Department detective wrote in the affidavit.

Decorated rocks honor the victims of the shooting at Robb Elementary School in Uvalde, Texas, Wednesday, May 3, 2023. AP Photo/Eric Gay

The teen is charged with making a terroristic threat to the public, which is a felony, and a terroristic threat to his family/household, a misdemeanor, jail records show.

His cousin, who was 18 when he carried out the massacre at Robb Elementary School, was killed by police at the school. Law enforcement officers waited 77 minutes to confront him, however; in the year since the shooting, many have blamed that wait on the former chief of the school district’s small police force.

A Washington Post investigation in May found that at least seven officers – who were still employed as of this spring by the same agencies for which they worked that day – delayed as it became clearer that the students and teachers inside the school were still in danger. Records also showed a chaotic medical response, including helicopter and ambulance delays, as victims of the shooting lost blood.

Several mass shootings have been carried out in Texas since the one in Uvalde. A mass killing at an outlet mall in a Dallas suburb left eight dead in May. In April, a man was accused of fatally shooting five neighbors, including a 9-year-old, with an AR-style weapon.

At least 159 people have died in 32 U.S. mass killings this year, according to a database maintained by the Associated Press, USA Today and Northeastern University. The Washington Post defines a mass killing as an event in which four or more people, not including the shooter, have been killed by gunfire.