Story highlights Sierra Bradway's dad, a police officer, was killed in the line of duty in 2013

She got a surprise Saturday when dozens of police officers joined her for her prom photo

(CNN) Sierra Bradway had planned to take her prom photos at the gravesite of her father, an Indianapolis police officer who was killed four years ago in the line of duty.

She had no idea that anyone, besides her date and a photographer, would be there.

But when she and date Brock Spayd arrived at Indianapolis's Crown Hill Cemetery on Saturday, they were greeted by dozens of police officers who had come to help pay their respects.

The plan was set in motion by Brock's mother, a captain in the Marion County Sheriff's Office, who learned of Sierra's cemetery visit and called upon officers from the Indianapolis Police Department and other regional departments to help make the teen's prom more special.

A video posted on Facebook shows a stunned-looking Sierra stepping out a white SUV to find two police officers on horseback and a crowd around her father's grave.