[CalRepublican]

I get that, but how do armed guards assigned to keep people with weapons out of the courthouse not manage to keep a man that has just killed three people inside the courthouse?

[DGray]

I just tried to do a text diagram to explain my memory of the entrance/exit, but it didn't look very good in the preview. So here's how I remember it: the entrance and exit are basically side by side and separated by a low wall or other barrier. On the entrance side there is a security station with x-ray equipment and all that, manned by several deputies who as I recall were very alert and on-the-ball. The exit side was manned by a station which I never saw manned by more than one deputy and I never was stopped going on out nor did I see anyone stopped. There were however numerous deputies patroling in the general vicinity. I never noted any deputy being lax.

Someone may have more recent and/or detailed knowledge, but that's what I remember about it. I think the perp was a) very clever and b) had a bit of luck on his side.

[Ramius]

I get that, but how do armed guards assigned to keep people with weapons out of the courthouse not manage to keep a man that has just killed three people inside the courthouse?

He used the stairs, down to what was likely a fire exit.

[ArmstedFragg]

The deputy killed in front of the courthouse was attempting to stop him from fleeing. It's not uncommon for a crook to flee before the word gets out. The exit stairwell was apparently right next to the courtroom, and there would have been a bit of a delay before the alarm was raised.

The implied supposition in your question most likely doesn't match the facts in this case.