ELP Tower Controller reported aircraft failed to follow SID resulted in entering a higher MVA and a CFTT event.

Narrative

I was working Local Control. I cleared Aircraft X for takeoff he was filed a SID departure. Off the departure end of the runway I switched him to Departure because it appeared he was doing the departure. Once he was a mile away I realized he was not following his departure procedure he appeared to be going runway heading towards terrain so I called Radar and informed him he didn't look like he was turning. Radar informed me he never switched to Radar. I called out to the pilot he answered back so I told him to immediately turn left heading 100 for terrain and maintain 170 altitude he was in a 080 MVA at 060 he appeared to be taking the turn but slowly so I gave him a left turn heading 070. I brashered the pilot for not following his departure clearance. I forgot to give the pilot an Low Altitude warning during my rush to get him away from the terrain. I would recommend telling the pilots to depart the SID they are given even though they should already be following there clearance guideline.