Locked Up! The Proof Of Orlando Shooter's Dark Family Past Exposed

As the investigation into the deadliest mass shooting in United States history continues, RadarOnline.com has learned that Omar Mateen's horrific massacre Sunday morning was not his family's first run-in with the law. As RadarOnline.com reported, his mother was previously arrested for battery against his dad — and RadarOnline.com has the photo proof!

Omar's father, Seddique Mir Mateen, continues to insist that theirs was a normal family, with no signs it could produce a cold-blooded killer. But a hint at Omar's haunted past is suggested by his mom's mugshot, taken at the Martin County Jail.

The deranged gunman's mother, Shahla Mateen, was taken into custody after she allegedly attacked her husband while he was brushing his teeth on the night of Dec. 7, 2002.

"Victim Seddique Mateen told me that both his wife and he has been arguing and when he went to brush his teeth his wife, the above defendant, started cussing at him and pulled his hair along with pinching his left bicep," the responding police officer wrote in her arrest affidavit.

The cop also noted that Seddique's injuries were obvious upon responding to the domestic dispute.

"The victim Seddique had a visible red mark on his left bicep consistent with being pinched," the document states.

At the time of the incident, the couple had been married for 20 years and had four children together. According to the paperwork, they were in the home during the brutal assault.

Seddique later dropped the charges against his wife and the case was dismissed.