So this article makes it seem like he's got dementia and was under the spell of a delusion when shooting his partner & daughter. But it's written so vaguely that it's hard to know for sure. So I found another article that seems to be much more clear about what happened:
TL;DR: 66-year-old man is in rough shape; has Hepatitis B, Emphysema, and COPD, and needs an oxygen tank. His partner (a much younger woman), their daughter together (8 years old), and his son from a previous marriage (18) all came to his house. The article doesn't say what happened in the conversation, but he apparently became enraged thinking they were trying to get him out of the house. My guess is that they were trying to get him to go into a care facility due to his many, many ailments.
Dude saw red, grabbed a gun, and started blasting. Shot his partner, then tried shooting his son, missed, and hit his 8-year-old daughter in the back as she was running away from him.
So it sounds much less like dementia (though that could still very well be a factor), and more like a miserable piece of shit reaching for a gun first to solve all of his problems.
I'm not saying it's better or worse, just that it would be a different story. Dementia changes people. My grandmother went through it; she was an incredibly sweet person before Alzheimer's, and then once she started sunsetting, she became vindictive and paranoid. Thought people were plotting against her or trying to poison her.
I posted this update because the original article was really badly written, and it was hard to figure out what actually happened.
I think a lot of people commenting have been fortunate enough to not have a loved one, or even someone they are close to succumb to these ailments. I’ve had a relative and two older ladies I grew up with pass away as completely different people than they were during the 30+ years I knew them. The hatred, vitriol, unhinged, and unprompted behavior was gut wrenching. Their sadly wasn’t much of a support system other than what they could get with Medicare and the community of people that only stuck around due to who they were rather than what they had become. It rocked my world and was life changing on my outlook on a great number of things to see in person how the most loving, sweet, caring people I could ever imagine knowing turn into monsters. Two of these women would start baking cookies for us kids growing up if we stopped by unannounced and loved nothing more than an unprompted visit turned to an evening of cards. Their last 3-5 years of life was not who they were, it was a disease, and it was scary.