Kim Zolciak's Son Alleged Sexual Battery Case: Cops Pulling Security Footage, Cell Phone Data

The police investigating 'Real Housewives of Atlanta' alum Kim Zolciak's son Kroy Biermann Jr. for an alleged sexual battery say they went out to the scene of the alleged crime to obtain evidence ... and they saw him and the alleged victim on video.

According to court docs, obtained by TMZ, the Alpharetta Police drove to the gym where Kroy Jr. allegedly forced a girl from his school to put her mouth on his penis. She also claims he digitally penetrated her despite telling him no numerous times.

The officer says he reviewed security footage from the gym ... showing the alleged victim arriving and later hanging out with Kroy Jr.

According to the docs, the video shows the girl leaving the family changing room, where the alleged incident happened, and heading towards the lobby … while Kroy Jr. left the family changing room and walked alone to the sauna.

Cops say they also spoke to the alleged victim at the police station, where she told them she knew Kroy Jr. and his girlfriend from school.

Cops say she told them Kroy Jr. had dated a couple of her friends but most recently began dating her best friend.

She told officers she blocked Kroy Jr. and his girlfriend after the incident.

The docs say the alleged victim gave cops permission to download the data from her phone, but the phone apparently had a broken USB-C port, which prevented cops from pulling the data.

As TMZ first reported, Kroy Jr. remains behind bars after being arrested on August 17.

Kim denied the allegations against her son, telling TMZ in a statement ... "The allegations being made against my son are nothing short of reckless and deeply troubling. He categorically denies ever being involved with this woman or engaging in the conduct she has alleged."