I don't usually participate in online discussion forums.  It's just sort of a "been there, done that" kind of thing and I'd rather use my online time doing the blogging bit.  However, this post is in reference to a thread at the USCCA Forum.  Don't bother clicking unless you're a member, because only paying members can read it.  I'm not going to quote the whole story, but I think I can get away with quoting the pertinent bits.  Fair Use, and all that.

The poster relates his first interaction with a law enforcement officer while carrying.  This interaction occurred because the poster was witness to a crime.

The poster begins, "First, I have to make it clear that I have nothing but respect and appreciation for LEOs and those who work in related fields."  This shouldn't even be important to the topic of the post, unless he intends to criticize a LEO or LEOs.  So why did he say it?  We'll see.
When exiting the store (7:38pm CST) and scanning the area, I noticed a man to my right, who immediately clicked in my mind as being a concern, just a gut feeling. I gave the guy a good stare to let him know I was a sheepdog. (Wanted to use that line since I first read it!)
Like one of the commenters said, "What does this even mean?"  He probably thought you were just some weird freak just giving him the eye.

As the story continues, it turns out that this man who was a "concern" was there to slash someone's tires--an employee of the store, it turned out.
I backed out of my parking spot to get into a position where I could observe his license plate number as he left; at this point he was slicing the back tire of the truck.
Good. That's where he should have stopped. A license number and a description of the perpetrator was all that was required. Sure, it was an act of crass vandalism, but it was targeted to a specific person and the welfare of not one person was endangered.

Here's where our strip-mall ninja hero screws up, big time.
I waited as he entered his vehicle and started to back out. Honestly, I made the mistake of assuming he would leave in the direction away from me, going around the back of the strip mall. But no this BG backs out and starts to come in my direction, before I knew what I was doing I'd turned my car to block the lanes so he couldn't get any closer to me. I then decided to exit my vehicle to have the option of either getting out of the way if he decided to ram me and/or have more cover options should this turn into a gun fight. I was carrying my XD in the small of my back and at this point I'm standing behind my car with my hand on my gun, ready but not drawn, there is about 15 feet between my passenger headlight and his bumper, he is stopped. I can now clearly see there is also a female occupant. I decide that if his engine revs my gun is going from holstered to drawn and on target. Lucky for both of us, he took the option of backing up down the lane. I re-entered my car and followed as he reversed. The portion of the parking lot behind him is completely empty, large ditch and empty parking spots to his right and strip mall to his left with a service drive at the rear of the building. I followed him at a good distance, hoping he would pull a 180 exposing his license plate, he did and I stopped, not turning down the service drive. I wrote down the license plate number turned to return to the front of the store and started to dial 911...
"Before I knew what I was doing"??? What's the matter, cowboy, your brain has a mind of its own?

So, it's true that an act of vandalism has been committed.  But who is initiating force here?  I think the answer to that is clear.  Our mall ninja first blocks the perp's initial path of escape, gets ready to start shooting if this person gets too close to his car--after he has blocked the guy's path--and then follows him when he leaves by another route.  There is another person, a woman, in the vandal's car who has not so far committed any transgression.  How does mall ninja guy know that she's even there willingly?

It seems to me that if Mr. Ninja had begun shooting, he would have had absolutely no defense against prosecution--nor would he have deserved any.

The rest of the post just goes on to recount his interaction with the LEO, which isn't completely relevant to my topic.

The majority of commenters at the USCCA Forum raked him over the coals for this.  His last reply to the comments gives me the impression that the advice he originally solicited had about as much effect as dirt clods thrown at a fence post.  A few grains might stick, but eventually it all blows away in the wind.  I wonder if he realizes that this post could even be used against him if he's forced to use lethal self defense in the future.  If his first-person report of this incident is accurate, he is obviously someone who is actually looking for trouble.

I would not go so far as to agree with some of the commenters who said he has no business carrying a gun, because even idiots have the right of self defense, but he definitely needs a trip to the woodshed.

I think when he at first said, "First, I have to make it clear that I have nothing but respect and appreciation for LEOs and those who work in related fields," he was thinking, "but I was there with a gun and they weren't so obviously I needed to do their job."

I would never have put myself into a situation like this.  I would have done my best to get the guy's license plate and a general description of him.  And then I would have probably driven to the far side of the parking lot before I called it in.  Why?  Because I want my children to grow up with their father.  I want to grow old with my wife.  I'm not going to put myself in danger.  Someone else is going to have to put me (or another innocent) in danger.  I don't ever want to use my gun against another person unless there is no other option.  This poster had plenty of other options, and intentionally putting himself into this dangerous position was wrong.  If I ever do anything so stupid, I hope one of my cherished loved ones gives me the severe butt-whomping I will so desperately deserve.

UPDATE:  Just to clarify my opinion (in case someone actually cares).  I personally would have had no gripe with Our Hero if he had threatened lethal force to prevent this crime from occurring.  Some people might.  He may or may not have gotten away with it, depending on where he was.  But I personally (I repeat) would have no problem with that.  However, that's not what he did.  He sat there and watched the crime to its completion and only then tried to put himself in a position to have an excuse to use lethal force.  This, to me, seems like someone who isn't interested in stopping an act of violence.  It seems more like someone who was just looking for an excuse to shoot someone.