10:42 AM PT -- The NFL tells us they are "looking into the matter."

6:00 AM PT -- Zay Jones was released from custody Wednesday morning at 4:45 AM. We're told his family picked him up. He's currently out on bond.

Buffalo Bills wide receiver Zay Jones got into a bizarre naked struggle with his brother -- who's also in the NFL -- and it ended in a bloody mess ... with Zay in handcuffs.

TMZ Sports obtained this video of the crazy fight that went down Monday night in a downtown L.A. apartment building. Zay is stark raving nude while grappling with his brother -- Cayleb Jones of the Vikings.

You can hear Zay yelling, "I'm going to fight for Jesus" ... and according to witnesses, Cayleb was trying to stop him from jumping out a 30th floor window.

Zay eventually broke free, and ran in the direction of Cayleb's gf's apartment ... you can hear her screaming. We're told at some point, he ran back out of the apartment, entered a public balcony area and smashed his foot through a window.

Photos from the scene show blood on the shattered window, and all over the floors and walls.

We're told Zay actually tried to squeeze through the hole in the window, but Cayleb restrained him until police arrived, and arrested him for felony vandalism.

Jones was the Bills' 2nd round draft pick last year.

According to law enforcement sources, he's being held in the medical ward of L.A. County Jail. It's unclear what his condition is at this point.

The Bills tell TMZ Sports, "We are still in the process of gathering more information on the matter. At this point, we will have no further comment.”