A holster for a handgun that comprises a holster body with a handgun cavity for receiving and retaining the handgun by way of a obstructing member at the ejection port and at the rear portion of the handgun slide. Moreover, a single obscured push button actuates both mechanisms. An internal retention sleeve having an inverted U-shape is slidingly mounted within the holster body and movable between a first securement position and a second release position. The sleeve having an integral thumb button depressible downwardly whereby the sleeve moves downwardly within the body to release a ejection port stop catch and the latch hood. The sleeve biased toward a normal retention position, the handgun withdrawal obstructing member biased toward the normal retention position, the latch hood biased toward a release position but having a normal latched obstructing position until released by the sleeve.