BJ Penn Arrest Stemmed From Altercation With 79-Year-Old Woman, Cops Say

7:27 AM PT -- According to court documents obtained by TMZ Sports, BJ Penn's mom, Lorraine Shin, claims she's the 79-year-old at the center of the allegations against the MMA legend.

In the docs -- which were part of an application written by Shin for a restraining order against Penn -- Shin alleged Penn is suffering from a psychological disorder that's caused him to believe she "killed his family" and has "taken over his mother's identity."

Court records show a TRO was granted in the case -- and both parties are due to appear before a judge on June 10 to share their sides of the story.

Cops in Hawaii say MMA legend BJ Penn was arrested over the weekend not just once, but twice, over multiple incidents he had with a 79-year-old woman.

The Hawaii Police Department tells TMZ Sports ... the first encounter Penn had with the elderly lady went down on Sunday in Hilo at around 8:45 PM.

Cops say the woman told them "Penn took her mail and then shined a bright flashlight in her eyes when she asked for the mail to be returned." They added the woman told them she was later shoved against a car by Penn after she attempted to move the light away from her eyes.

Penn was arrested over the allegations and booked on a charge of abuse of family or household member -- but he was released a short time later after posting bond. He was given a warning citation -- which ordered him to stay away from the alleged victim -- but according to cops, he violated it just hours later on Monday morning.

46-year-old Penn allegedly showed up to the 79-year-old's home following his release -- which led to another arrest. Cops tell us he was booked on another charge of abuse of family or household member -- and jail records show he remained behind bars until Monday afternoon.

Once out of custody, Penn took to his Instagram to share video of his Sunday run-in with cops. In the footage, you can see officers trying to drag Penn out of his bed ... all while they told him he was being arrested for "harassment."

In a caption on the vid, Penn wrote, "In Hawaii, 'impostor theft' refers to instances where individuals falsely impersonate others, often to steal their identity or commit fraudulent acts. This can involve using a fake identity to obtain documents, financial accounts, or even posing as law enforcement or other professionals to commit crimes."

On Tuesday, he posted another video on his IG page titled "FAKE LORRAINE SHIN." The footage appears to show someone waving a light, all as a woman screamed, "hit me!"