Up next the killer is hunting law enforcement. He's murdered right outside the courthouse. I was just amazed and shocked.

Possible targets are on edge.

I felt like there was a vendetta against law enforcement as a whole.

This hit very close to home.

That attack was very brazen.

But the killer's own arrogance creates the clue that exposes him.

We had our evidence.

Just a profound sense of relief that we had our guy.

It was kind of a mix of Christmas morning and the Texas Rangers went in the World Series. So, Kaufman, County, Texas, is close to Dallas, yet retains many of the down home qualities Texans still hold dear.

But proximity to Dallas is not without its cost and Coffman City, the county seat, sees more than its fair share of crime.

It's kind of like Mayberry, that Mayberry with methamphetamine maybe and the Aryan Brotherhood.

Just by being situated close to Dallas County, they get a lot of that big city crime slopping over their county borders.

On a January morning in 2013, it was business as usual around the Kaufman County Courthouse.

The time of day this is the time when the courthouse really starts to come alive and

in the square itself comes alive.

For Mark Hasi, a well-respected prosecutor, it looked to be a regular day at work.

As Mark made his way to the courthouse, a man came up to him and appeared to confront him.

Linda Bush, a prosecutor and a former police officer, saw all of this as she was parking her car.

Mark was walking toward the courthouse.

As they got closer to each other, the person who was walking toward Mark shoved him.

Within seconds this became much more than a shoving match.

The men who'd approached Mark pulled out a pistol, pushed it into Mark's neck and shot him five times.

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