"The only ventilation was the door, the one entrance and exit when it was open," says Yavapai County Sheriff Deputy Lt. David Rhodes.
Eyewitnesses say Ray was seated next to the tent's flap, so he could get fresh air when it was opened after each 15-minute session. Fresh air was a luxury many others did not enjoy.
It was not long before the trouble began.
One participant tripped and burned his arm on the stones. "His skin was gone, and the skin was just basically hanging off of his elbow," recalls Martin, who had been stationed outside the tent. "And I was trying to take care of him and his entire mind was - his mindset was getting back into there. He said I'm not done. I've got to go back in."
That man went back into the tent, but others started to stream out of the lodge in abject panic.
"It just looked like these people had been hit by a car or something. I mean, they were on their side -- laying on their sides, barely breathing. It was unbelievable. I've never seen people in such a bad condition.
Those still inside the sweat lodge tried to remain positive and heed Ray's catchphrase to "play full on."
But not everyone would make it out alive.
"People were coming out, uh, screaming, saying, you know, things like...I'm dying, I'm dying, please don't let me die, said Amstel.
Meanwhile, Essad says, Ray responded, "You're more than that, you can push through this."
Outside the sweat lodge, Amstel saw a friend collapsed on the ground. She says Ray's staffers told her to stand back.
"They were like, you know, you need to leave her alone, that's her experience, you don't wanna intrude on her experience, so you sit there and just be quiet," she said.
Many still inside the lodge disregarded what their own bodies were telling them. Among them, Kirby Brown.
Investigators later told Brown's mother that her daughter had been in distress for some time before she was removed from the tent.
At some point, someone called out, "Kirby isn't breathing, Kirby is having trouble breathing," Brown said she was told.
She said Ray's response was, "We will deal with that at the end of the next round."
Eyewitnesses say it wasn't until about 20 minutes later that Brown was finally carried out. By then, she was completely unresponsive.
"He didn't direct anyone to help her," Brown said. "People were being pulled past him unconscious... and he continued this exercise."
"It was quickly becoming like a MASH unit," said Martin.
Martin says her fellow staffers told her not to call 911 because it would upset Ray. Eventually, however, someone made the call.
When paramedics arrived, they wondered if they'd stumbled upon a mass suicide, according to Martin.
When Ray finally exited the ceremony, he seemed not to be aware of the gravity of the situation.
"He stretched his arms up and was hosed off, Martin said. And he's like, 'Hey, thanks.' And his assistant came out, and they just looked amazing."
"I just stopped and I said, how can you walk out of there when all of these people…they look near death, and you guys can walk out there looking like you just spent the day in a spa?
Martin recalls that as she performed CPR on Kirby Brown, her boss simply stared.