Well maybe you can give us a link to the Irvine police department arrest record for Ahmed. You should have no problem finding it.
But no. I don't think you can be arrested without charges. You can be detained for questioning without charges however.
It's not going to be in Irving TX. Dallas County would have the record of the arrest on it's website if it did happen. But it's not uncommon for it be unlisted but 'in the system' with him being a minor. I know my arrest form ten years ago (for marijuana ashes in a car that wasn't mine) is not listed in their data base, while my dads from some thirty years ago is. That's just typical Texas for you, and why I'm very skeptical of the professionalism of the cops in this case.
And yes, it would be more accurate to say that one can be
detained without charges, rather than arrested.
It's really the same thing in principle. Police can still hold you up to a full day without formally charging you with anything - it's mainly a method of buying time for the police to go through the book, and come up with something.