Texas active duty soldier illegally arrested and disarmed

Yesterday morning I woke up to a text from my best friend with this video attached and while it is not my video I felt that you should be made aware of it.
Texas police arrested an active-duty Army sergeant for “rudely displaying” a hunting rifle. The sergeant, C.J. Grisham, established an online legal defense fund after he was, in his words, “illegally arrested and disarmed” for carrying the firearm.
In the video the Sergeant asks why he is being disarmed and detained; this was after being told that the officers were called out by a citizen reporting a person carrying a rifle, Sergeant Grisham asks the officers if they explained to the person reporting that Texas is a “Right to Carry” State, the officer had this to say:
“They don’t care what the law is,” the officer replies. Grisham then shoots back, “Do you care what the law is?”
“In this day and age, they’re alarmed when they see somebody with what you have,” the officer replies.
“Just because a guy has got a firearm, he’s dangerous?” Grisham asks, drawing the reply, “Yes, sir.”
Afterwards Grisham says that he feels threatened that the officer has a weapon, to which the officer replies that he is “exempt from the law”
Below is the excerpt from the video Sergeant Grisham released on Youtube explaining the situation along with the actual video of the altercation:
On March 16, 2013, my son and I were hiking along country roads among pastures and fields with my 15-year old son to help him earn his hiking merit badge. I always enjoy these father/son hikes because it gives me time alone with my son. As I always do when we go on these hikes and walks, I took my trusty rifle with me as there are coyotes, wild hogs, and cougars in our area.
In Texas, it is legal to openly carry a rifle or shotgun as long as you do so in a manner that isn’t calculated to cause alarm. In other words, you can’t walk around waving your rifle at people. I always carry my rifle slung across my chest dangling, not holding it in my hands.
At about the 5 mile mark of our hike, a voice behind us asked us to stop and the officer motioned for us to approach him. He got out of his car and met us a few feet later. He asked us what we were doing and I explained that we were hiking for my son’s merit badge. He then asked me what I’m doing with the rifle, to which I responded in a calm manner, “Does it matter, officer? Am I breaking the law?”
At that point, the officer grabbed my rifle without warning or indication. He didn’t ask for my rifle and he didn’t suggest he would take it from me. He simply grabbed it. This startled me and I instantly pulled back – the rifle was attached to me – and I asked what he thought he was doing because he’s not taking my rifle. He then pulled his service pistol on me and told me to take my hands off the weapon and move to his car, which I complied with.
He then slammed me into the hood of his car and I remembered I had a camera on me (one of the requirements of the hiking merit badge is to document your hikes). This video is the rest of that encounter. Up to this point, I am not told why I am being stopped, why he tried to disarm me, or even that I’m under arrestwatch the video.