User blog comment:Commdor/Game Informer ME3 Preview (Feb. 2012)/@comment-3053284-20120110110727/@comment-743796-20120110121524

Unlikely as it seems, because the protheans were the most advanced pre-modern species in the series. Additionally, the descriptions for the GRV and DR mention that whichever race fired the shot no longer exists, so either it is the protheans but this fact is unknown, or this was a predecessor of the species.