racerlinkfc

i was on the way home last night from work as i get off the off ramp i proceed to stop at the light , i tried putting into gear and the damn thing would not budge into gear ! so i had the car towed and checked my tranny fluid resevoir it was completely empty . can anyone offer any ideas to what might cause this i already checked the clutch line to the master cylinder . sorry i've never had this problem .oh one more thing its a 1988 mazda rx7 n/a any insight would greatly help .