How did Agnes' grandmother die?

WARNING: Just a quick disclaimer. Some readers may find this offensive due to an traumatic event. Please do consider that this was a work of fiction. Names, characters, places, and events are the product of the author's imagination. Any resemblance to actual events, locales, or person (living or dead) is coincidential. 

For the continuing chapter of the "Saturday Routine", today I had published another chapter entitled, "When No One Cares." It was now revealed how Agnes' grandmother had died and how she dealt with it. However, I might not tell you the whole story how she really dealt with it after and that's why where going to talk about it now. And also to clear out that it was her father's mother.   

Before 

It all started back in 2013 when she was only 12 (almost 13), when she had started feeling down. Her grandmother‒Lethisya, who had been diagnosed with heart disease had reached out to Agnes due to the grieving of the death of her daughter. Agnes had spent a month of her summer vacation at her grandmother due to her request and spend their time being together. Agnes' relationship with her grandmother had grow deeper to the point she had finally told her that she wasn't okay. 

Agnes and Lethysia had took their conversation at her kitchen an right after Agnes told her, the phone suddenly ring and so Lethysia took the call from the other room. When Agnes had suddenly heard a porcelain crash against the floor from the other room, she took no doubt and ran towards the other room where her grandmother took the call. And there she saw Lethysia laying unconcious at the floor. 

After 

Right after Agnes called 911, she called her parents. Once the ambulance came in their house, Agnes' parents came. They took Lethysia at the ambulace while her parents took Agnes at the car. Lethysia had been declared dead right after they arrived at the hospital. Agnes' parents blamed her without asking her any questions and so she lived with that guilt for her entire life. 

And that became another reason why Agnes won't join them on breakfast. For the reasons that she's been buried by her own guilt. 

“And yes, you can tell me that I’m too young to not join my parents on breakfast, you can me that I’m too young to be by myself. But do you know that how it feels like?” I questioned him as I felt a single tear squeezed out of my wild eyes. Nevertheless, I wanted to question myself, why now? “To be blamed?”