AUSTIN (KXAN) — Authorities arrested a 17-year-old girl this week and accused her of making online threats against a northeast Austin elementary school, according to the suspect’s arrest affidavit.

The FBI received a tip about an Instagram user, later identified as 17-year-old Giana Castillo, “making concerning statements online… regarding the planning of an active shooter event,” at Graham Elementary School. FBI agents tracked the IP address of the account to Castillo.

While analyzing the account, investigators found “the user had an active interest with previous active shooters and posted concerning statements,” according to court documents. The affidavit also stated she planned to kill her family members before going to the school’s campus.

The arrest document indicates Castillo attended Graham Elementary School from 2013-2017.

According to court documents, “AISD was notified of the threat to one of their elementary schools which caused an emergency response.”

Castillo was arrested Tuesday night, court documents said. According to a joint statement from AISD and the Austin Police Department, Castillo’s parents are “cooperating with law enforcement.”

Due to the threat, AISD added increased patrols at the Graham Elementary School campus. Castillo faces one charge of making terroristic threats. This is a third-degree felony.

Online court records show she was booked into the Travis County Jails, and her bond was set at $100,000, according to inmate records.

NewsNation affiliate KXAN has reached out to Castillo’s attorney and will update this story when we get a response.

The Austin Independent School District sent a letter home to parents stating that the Austin ISD Police were contacted by the FBI “about an investigation into an online threat that was made toward our school. The FBI had already located the suspect and made the arrest before the start of our school day… While we understand there were plans to cause harm, our local law enforcement was able to intervene swiftly before any plans could more fully develop.”

The school will hold a meeting Monday to discuss safety protocols, according to the letter.

The case remained under active investigation Friday, and no other details were released.

How law enforcement was notified

The Austin Regional Intelligence Regional Intelligence Center (ARIC) School Safety Symposium that was recently offered to public entities earlier this month is how they were all informed of the incident, the statement from AISD and APD said.

“The goal was to create constant collaboration between public safety, ARIC, federal partners, mental health professionals, and educators, to keep each other informed of potential threats prior to an event happening,” the statement said.

Both agencies said this “credible threat was stopped, a suspect was quickly identified, and taken into custody.”

We’re committed to keeping our community safe and have taken measures to prevent any threats. We’re currently recruiting and onboarding additional police officers in compliance with HB 3 to expand coverage districtwide, including at every elementary school. Last year we also partnered with the Travis County Sheriff’s Office to use the old Rosedale School facility as a training center for active threats on campus. We’ll continue to work regionally to prepare for any threats, including completing annual tabletop crisis exercises with regional law enforcement, partner organizations, and healthcare teams to ensure in the case of any crisis, we’re able to quickly respond.

Austin ISD Police Chief Wayne Sneed

The joint statement said the partnership with APD, the FBI and AISD Police prevented a “possible tragedy” and the “community remains safe.”

Partnership is a pillar of effective law enforcement and essential to everything we do. We appreciate our partners at the Austin Police Department and the Austin ISD Police Department, who continuously work with us to make sure kids in Austin are learning in a safe environment. They share our dedication to protect the people of Texas. We depend on individual residents, our private sector partners and others in the community to speak up and report it when they notice something suspicious. We encourage everyone to visit FBI.gov/prevent to learn more about preventing mass violence. Together, we can make a difference and stop those who seek to do harm in our communities.

Special Agent in Charge Aaron Tapp of the FBI’s San Antonio Field Office

“The Austin Police Department and our partners, encourage anyone that sees or hears something suspicious or out of the ordinary, to report it immediately by calling 9-1-1,” the statement said.