VLA observations of the triple radio continuum source in Serpens have revealed its extraordinary characteristics. While it is associated with a star-forming region, its outer components exhibit nonthermal spectra and large proper motions. Here, we present the results of high-sensitivity, multifrequency VLA radio continuum observations of this source. These observations show that (a) the radio source consists of a central component, and two lobes with enhanced brightness at their ends; (b) there is knotty and extended emission connecting the central source with the outer NW component which we identify as a radio jet; (c) the central source exhibits an almost flat spectrum with a spectral index alpha = 0.15 +/- 0.09, the NW component also has a flat spectrum with an index alpha = -0.05 +/- 0.05 (characteristic of optically thin thermal emission), and the SE component has a negative index alpha = -0.30 +/- 0.04 (consistent with nonthermal synchrotron emission); (d) the outer sources break into a number of components (which we identify as ''internal working surfaces'' or ''bullets'') with similar tangential velocities and directions; and (e) the central source has an elongated morphology, with its major axis nearly parallel to the outflow direction but having a significantly different direction, which suggests that the central source may be precessing or nutating. These observations confirm the unusually large proper motions of about 0.12'' yr-1, previously measured for the outer NW and SE components. Moreover, similar proper motions have been obtained for a time-variable knot in the NW radio jet, suggesting that probably all the knots in the body of the jet have velocities similar to those of the outer components. The spectral indices of the main three components differ from those obtained previously. We suggest that the brightness variability of the outer sources, as well as the change in their spectral indices, could be the result of the passage of locally enhanced condensations through the bow shock produced by the ejected bullets. We find that if the NW and SE clumps are moving through a medium with density of n0 approximately 10(5) cm-3, then the thermal free-free emission produced by the shock waves around these objects can account for the observed emission. However, a nonthermal particle acceleration mechanism is required to account for the negative spectral indices. We identify the triple radio continuum source in Serpens as a young radio jet, with a dynamical age of only approximately 60 yr, emanating from the central component. This radio jet exhibits a one-sided morphology that is very similar to that observed in optical Herbig-Haro jets, suggesting that jets associated with young stellar objects are intrinsically unipolar within the dynamical ages of the main jets and not an extinction effect. We believe that the knotty structure in the NW radio jet and the SE components are the result of discrete ejection of material (or ''bullets'') from the central source. Finally, based on the morphological and kinematical similarities between this radio jet and optical Herbig-Haro jets, and their different length scales and dynamical ages, we propose that the Serpens radio jet could be a proto-Herbig-Haro system, in an early stage of evolution.
