The drill, which was planned months ago, took over a floor of the former St. Francis Hospital in Beech Grove, RTV6's Stacia Matthews reported.

In the scenario, a man approached the nurses' station asking to see a patient. But when he was denied, he quickly became aggravated, pulled a gun and began shooting.

"Unfortunately, that's what happens. There's not a lot of indication from the people beforehand in these issues, and the tipping point, once that tips, you have bad consequences," said Indianapolis police Sgt. Brandon Cooper.

As part of the drill, the gunman made his way down the hall and fired into patients' rooms.

Organizers said mass shooting training can be crucial, especially in a hospital where most potential hostages or victims would already be sick or weak.

Curiosity got the best of one of the volunteers playing a patient who stuck her head out into the hallway during the drill, something police said could have led to her death had it been a real threat.

"Shut the door and block it. Put anything you can to distance yourself and your loved one and the shooter," said Kirby Haskins, who helped develop the drill. "You don't want to give the shooter another reason to pull the trigger. If he sees your face, you're a witness."

Medical personnel, who are trained to help people in times of trouble, can also learn about protecting themselves, fellow staff members and patients, organizers said.

"Anytime we can get out of our routine our day-to-day things, I'm pleased with the results," said Rich Witmer with St. Francis Health security. "It will either confirm what we're already doing or point out things we need to think about for an actual scenario."

A debriefing was held after the drill. More exercises will follow to help health providers and law enforcement hone their skills for the best response.