A US teen has been arrested on the charge of plotting a mass shooting at her school in Indianapolis on Valentine's Day.

The arrested student was identified as 18-year-old Trinity Shockley.

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According to reports, she was arrested for conspiracy to commit murder, intimidation and conspiracy to commit intimidation.

She is being held without bond in the Morgan County Jail in Martinsville, Indiana, reported ABC News.

According to a probable cause filing submitted to the court, the FBI's Sandy Hook Promise Say Something Anonymous Reporting System contacted the local sheriff after a tipster said their friend was planning an attack, had access to an AR-15 rifle and had just ordered a bulletproof vest, the news channel reported.

The tip reportedly revealed that the teen was obsessed with Nikolas Cruz, the mass murderer who opened fire at Marjory Stoneman Douglas High School in Parkland, Florida, on Feb. 14, 2018.

During the 2018 attack, Cruz had killed 14 students and three attackers.

According to reports, during an investigation police, while searching the apartment of Shockley that she shared with her father, wall photos of Cruz, Dylan Roof and Andrew Blaze were found.

All three persons were involved in mass shootings in the past.

The teen's backpack was decorated with buttons of the killers' faces -- which also graced the wallpaper of her laptop, officials told ABC News.

Authorities also found a poster of the 2003 mass shooting movie 'Zero Day' in her room.

As the anonymous tip about "Jamie" suggested, Shockley's home contained AR-15 magazines, ammunition and a soft armour vest, police told the news channel.

Later, the arrested teen told investigators that she was "joking" about her plans.