Ex-NBA player Glen Rice Jr. allegedly beat up a former NCAA hoops player so badly, he broke the guy's jaw and knocked a tooth out ... this according to the police report, obtained by TMZ Sports.
We broke the story, Rice was arrested on July 25th in Georgia -- and according to the police report, one witness watched the violent scene unfold.
The witness told cops ... Rice and ex-Tulane player Jordan Callahan pulled into a Kroger parking lot in a white Porsche ... and got out of the car to have a conversation.
During the exchange, the witness says Rice clocked Callahan in the face -- knocking out the guy's tooth. The witness says Rice grabbed 2 bags from the car and ran down the street.
When cops arrived, they found Callahan in a pool of blood -- and the witness pointed to where Rice fled. Cops tracked down Rice and arrested him ... and found 2 bags nearby, hidden under leaves.
Inside the bags -- 2 guns (an AK-47 assault rifle and a Taurus .38 Special) and a bunch of bullets.
Cops say a 3rd gun was found in the Porsche.
There's more ... cops say Rice also had roughly $2,700 in cash and 6 cell phones on him at the time.
He was initially booked for felony robbery, aggravated battery and marijuana possession -- but cops tell TMZ Sports officials are only moving forward with 2 charges ... aggravated battery and possession with intent to distribute.
Rice's lawyer, Steve Sadow, told TMZ Sports that he's "confident his client will be found not guilty" and pointed out that the robbery charge has already been dropped.