When someone threatens you on Facebook?

[...]

I know that Facebook is a place to stay connected with family/friends and maybe meet new people but I personally prefer to be private and stick with the people I know.
Some girl who I don't know and happens to have mutual friends with me on Facebook friend requested me and before I could look at her profile I realized that she had already deleted me.

My status are public and I decided to write this: "people who I don't know always add me only to go through my stuff, nosey weirdos"
After I wrote that I went to search for her name and when I came to her profile I saw her status saying something about killing me and my family and that she'll fight me for it..

Why was she still looking at my profile after she deleted me?
And why was she threatening me on Facebook of all places?
I don't know her and I reported her postings.
No messages have been exchanged between us but I feel like if this was a serious matter that she would indeed message me.

[Anthony]

If she posted something about killing you and you family, call the police. Thats really serious and hope your alright.

[Mixx]

report to fb or call police if about killng you ect

[Josephina cameron]

Call the police. What she did'was wrong.

[Makivka]

Consult with your family if you should call the police.
There are some hackers out there that can figure out where you live, but very few.
I believe it's a joke, or she might be mentally ill, so consult with your friends and family and give a call to the police.