The young Syrian, also known as Narraboth, is the captain of Herod's guard. He's also a romantic, hopelessly in love with Salomé. His crush is not only deep, it's also kind of child-like—it's because of this that he doesn't listen to the Page's warnings. It's also because of this that he can't bear to see Salomé (who he luuuurves) lust after Jokanaan. His naivety is at its most intense when Salomé convinces him to release Jokanaan. She plays him like a fiddle—and all it takes is the promise of "a little green flower" to make him weak in the knees.
That being said, his suicide complicates things a bit. He's not simply an innocent—he's an innocent in love with his own innocence, with his own unsullied beauty. "Also he had much joy to gaze at himself in the river," the Page of Herodias tells us. "I used to reproach him for that" (67).
This shows us that he's kind of a Narcissus, fascinated by his own image…and the image of Salomé that he seems to have created. In the end, he would rather die than see his darling flirt too much with someone else.