The Heckler & Koch UMP (Universale Maschinenpistole, German for "Universal Machine Pistol") is a .45 ACP submachine gun developed and manufactured by Heckler & Koch. The UMP has been adopted by various agencies, such as the U.S. Customs and Border Protection. Heckler & Koch developed the UMP as a successor to the MP5, though both remain in production.
At the apartment of Matt Farrell in Camden, New Jersey, one of the assassins working for Thomas Gabriel carried the UMP-45 machine guns in attempt to kill the hacker who unknowingly passed his portion of security code to the cyber-terrorists, led by Gabriel and Mai Linh. After New York cop John McClane killed two of his comrades, the assassin carrying the UMP-45 variant fired his way through the barricaded apartment door. He entered the apartment shooting up the place. Despite being shot in the leg, the hitman continued to fire at McClane. But when a toy figure hit the delete button on Farrell's keyboard, the pre-planted C4 explosive on Farrell's computer blows up, killing the assassin. McClane commandeers the UMP-45 gun from the dead assassin. McClane guards Farrell with it as they leave the burning apartment. After he escorts Farrell to his car, McClane puts the machine gun on the back seat. Then they took off, while McClane injures assassins Del and Rand after their own attempt to kill them.Gabriel's henchman, Emerson also carried the UMP-45 variant for a time being at Woodlawn. He takes that weapon to check out cooling tower 7 and leaves the server room with it. Then when he returns, Emerson points the weapon at Farrell when he encrypts the financial data on the laptop he downloaded to. But knowing he can't kill him since he encrypted the data, locking out access to it, Emerson takes Farrell to Gabriel to crack the encryption. He takes hostages Farrell and Lucy McClane to the HAZMET truck before leaving to head for the warehouse hideout.