Grace was a nurse who worked in a private hospital, which was a specialty hospital specialized in neurology. She worked 12-hour night shifts and worked 3 nights a week. She also worked in a big name fast food restaurant. She liked working, she was a bit of a workaholic. She was a responsible person. People liked that about her, that they could rely on grace.
One day, as she was arriving at the hospital for her night shift, she saw police cars in front of the hospital. Apparently something happened. She found out from the police that someone with a gun is in the hospital, threatening the doctors to treat his sister for free. It was because he couldn't afford to pay for the surgery and his sister was dying, and he was angry at the doctors. His anger led to this reckless reaction.
Grace couldn't stop herself from going in there, because she felt a morbid responsibility to help the man with the gun. She knew that deep down he is just scared his sister might die. The police tried to stop grace from entering, but it was useless, she was fast.
When she reached the place of action, she tried to convince the man with the gun whose name was Jake to stop it. Grace promised Jake that she will convince the doctors to treat his sister. After their talk, Jake gave the gun to Grace and surrendered to the police. They did the surgery and saved his sister.
After the incident, one of the police officer asked Grace why she did what she did, and her answer was that she "feels a responsibility towards people who are in pain, and need immediate help". This sense of duty is to the point that she was willing to endanger her own life to save people.