In March 2020, a family on the Northern Cheyenne reservation in Lamedier Montana got shocking news about their loved one.

Christy wouldn't die.

My daughter came and notified me that Christy was run over.

And I said, it should be okay. And she's like, no, she died. I was like, what?

Missing justice from CBS News takes you inside what really happened that night,

and the federal investigation that followed.

Listen to Missing Justice from CBS News on Amazon Music or wherever you get your podcasts.

It was a complete mystery.

This is a shocking crime.

You know, the kind of shooting that you think you'd only see in the movies.

You could even call it a cold blooded ambush.

I'm Humella Argawe. I'm a reporter with CBS Los Angeles.

This happened in the mountains east of LA, way up in the mountains.

The sky dressed as a delivery man goes up to this home.

He knocks on the door when the guy who's supposed to take the package comes to the door.

He pulls out a gun and he shoots three or four times.

We didn't learn that the victim was a lawyer. His name was Mark Angelucci.

Angelucci died right there at the scene.

I couldn't stop thinking about Mark.

I would wake up in tears with my pillow already soaked.

Just knowing that I now live in a world without Mark.

I'm not missing him again.

...