It could be the brake fluid level if the light didn't go out when he lifts the parking brake pedal. If the parking brake shoes are adjusted properly, then the cables could be stretched. There is a finite amount of adjustment to take out the slack at the intermediate lever.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.