MEMPHIS, Tenn. (AP) — Police in Tennessee say a dead man’s body remained undetected in an impounded van for seven weeks.

Memphis Police Department Director Michael Rallings called Monday’s belated discovery “unacceptable” and said an internal investigation has been opened.

Rallings said robbers opened fire on the van after two men resisted robbery Dec. 18. The 47-year-old driver was shot multiple times, but the 55-year-old passenger was uninjured. Both men had told police that they were the only ones in the vehicle at the time.

News outlets report the car was impounded as evidence. The yet unidentified man’s body was found with a gunshot wound in the backseat when the driver came to pick up his vehicle Monday.

Rallings says an autopsy will determine if the man could’ve survived had he been found sooner.