This happened at the Slayer concert in Nampa, Idaho.
From the description:
"I took my mother-in-law to the Slayer farewell tour as she is an old metal head. She had never in all her years been into a mosh pit. I feel everyone should experience it at least once, so I took her in her wheelchair and asked a couple of big guys to help me keep her safe and off we went. She had the best time of her life."