I recently found out a very good friend of mine is in jail, how do i find his location in order to write him?

Long story short my sister's boyfriend whom I was very close with is in jail. My sister told me they broke up a few weeks ago, and I was upset, but I knew i'd see him again. I recently just found out he's in jail, and no one knows why.

I just want to write to him, telling him I still love him like a brother...

I know people can find police reports online but I can't no matter how hard I look. He's from NY, he lived in PHX AZ for a while, and then when he found out he was in trouble he came to NY and was arrested in NY and sent back to PHX. Is there any way I can locate which penitentiary he is staying at in PHX?

Thank you