TMZ Sports obtained the court docs with witness accounts of the incident and it's insane -- essentially saying Pryor and Briston got into a huge fight earlier that night that turned explosive.

A witness told cops ... Pryor, Briston and friends had gone out to dinner and drinks when the couple -- who have been dating for about a year -- began arguing.

Briston and her friends went to the club and Pryor went home -- but when the group got back to Pryor's place after partying, he was waiting in the hallway pissed off.

One female witness -- a friend of Briston -- told cops Pryor knocked her to the ground and began physically fighting with Briston.

The witness says Pryor and Briston "locked up" and "began to tussle."

The fight spilled into the apartment and into the kitchen -- and the next thing the witness saw was Pryor clutching his chest and bleeding.

Briston and her 3 female friends drove Pryor to the hospital where he was treated for VERY serious injuries.

In the docs, one officer says the female witness was voice texting into her watch and was overheard saying, "She was just defending herself and had to do it."

She added, "The only reason I'm here was to make sure that he didn't die" and "we should have just let him die."

4:17 PM PT -- Shalaya Briston was just released from custody -- and was covering her face as she went to a waiting vehicle. Our friends at WPXI shot video of Bristol as she left.

2:25 PM PT -- Cops say they found a semi-automatic pistol in the front passenger seat of Pryor's Mercedes-Benz ... along with a TON of blood inside the vehicle.

There's more, WPXI's Amy Hudak says cops also recovered a Glock pistol with a flashlight.

Hudak also reports a witness at the hospital was overheard saying, "We should have just let him die." Hudak says witnesses told police the two had a "very volatile relationship" and that Pryor "always had his hands all over her."

1:59 PM PT -- Terrelle Pryor has been arrested and charged with simple assault, according to the Pittsburgh Police.

Officials say the 30-year-old NFL player was involved in a "mutual combat" incident during a Nov. 30 dispute ... and the female involved has also been arrested.

24-year-old Shalaya Briston has been charged with Criminal Attempt Homicide and Aggravated Assault.

According to law enforcement, cops responded to UPMC Mercy Hospital to speak with Pryor, "who had arrived there in critical condition by private means just after 4:30 a.m."

Cops add, "Upon further investigation by detectives in the Violent Crimes Unit, it was learned the male's injuries were incurred during an earlier dispute inside an apartment on the 200 block of Heinz Street on the city’s North Side. During that altercation, a female victim also received injuries."

"After consultation with the Allegheny County District Attorney’s Office, police have arrested two people believed to be mutual combatants in this incident."