The home side looked as though they had the three points sewn up with just 30 minutes left to play, but were left stunned by four goals - the last coming in injury time.
"To sum things up, the first 60 minutes were brilliant from us, the last 30 were incredibly weak," said Low.
"Honestly, shortly after the game I can find no explanation as to how we let a 4-0 lead slip out of our hands.
"It's deathly quiet in the changing room. Players are laid out on the benches and are totally speechless."
Germany still top Group C with 10 points.