Brittney Griner 'Gay Baby Jail' Note Investigation Captured on Police Video

Law enforcement clearly took Brittney Griner's "Gay Baby Jail" note concerns seriously ... new police video, obtained by TMZ Sports, shows two cops intently investigating the matter.

The bizarre scene unfolded back on Feb. 17 at the Gaylord National Resort & Convention Center in Maryland ... after Griner told officials at the hotel she had discovered a handwritten message in her room that she found to be threatening.

Prince George's County Police body camera footage shows just a couple hours after the WNBA superstar hastily bolted from the area over the letter ... two officers rolled into the lobby in an effort to get to the bottom of the situation.

You can see in the vid, a hotel staffer showed them what the note looked like -- before he took them in an elevator to get to the room.

While on the way, the employee told the cops the message was taped to a door. He added that Griner was the one who found it.

Once inside the room, cops not only located the "Gay Baby Jail" message ... they also found a piece of duct tape on another door that read, "Private."

They ultimately determined the notes were likely left by the previous room's occupants -- who were in town for Katsucon, a convention for Japanese pop culture enthusiasts.

"The meme 'Gay baby jail' is used among people in the culture to describe a situation in which progress through a game is impossible," one of the officers wrote in an incident report after canvassing the scene. "In other words your video game character is gay (happy), baby (game character), and jail (can't escape)."