Can soldiers in civilian clothes salute a fallen comrade memorial?

I recently visited the Fallen Warriors Memorial on Cutten Road in Spring, TX. While I was there, I noticed a Veteran wearing a Vietnam hat and although I wanted to walk over to him and shake his hand, I decided to back off as he was paying his respects; however, prior to him leaving he stood in front of the memorial, came to attention and held a salute for a few seconds before bringing it down. So my question is actually coming from me as I've felt compelled to salute as well, but have refrained as I'm not sure what is correct.