Military
Air Traffic Control Fully Certified
Communication Breakdown; Situational Awareness
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert
Procedure; Human Factors
I had 2 aircraft on frequency landing at ZZZ. I had Aircraft Y on a vector for a visual at 5;000; and Aircraft X on a vector for an ASR (Approach Surveillance Radar) at 10;000. I issued a descent to 4;000 and a frequency change to ZZZ to Aircraft Y. Aircraft X read back these instructions. I caught a correct read back of the instructions but did not catch the incorrect call sign. Aircraft X was in an 8;700 MVA (Minimum Vectoring Altitude). I noticed the aircraft descending through 8;900; reached out on frequency then issued a low altitude alert when I observed him leaving the MVA altitude. Then on both UHF and VHF guard frequencies. Reached out to the previous sector to see if they came back and also to verify they were in fact IFR and not miss tagged. Center verified they were IFR and that they didn't have them. Aircraft X returns to frequency; ZZZ later said they sent him back when he came over to them. Once on frequency I again issued low altitude alert; verified he did have terrain in sight; and climbed them back up. At this point I did have the EVOM [Emergency Obstruction Video Map] up. We sorted out what had happened. I eventually descended him back in for the approach; switched to ZZZ; aircraft landed safely. The pilot misheard who the instructions were for and I missed the call sign on read back.
ATC Approach Controller reported miscommunication between aircraft resulting in aircraft descending below the MVA.