Cobra

An armed gunman causes a hostage situation at a Los Angeles grocery store. When negotiations between him and the law fail, Marion Cobretti (codenamed "Cobra") (Sylvester Stallone), a member of an elite division of the Los Angeles Police Department known as the "Zombie Squad", is summoned to the scene. Cobretti infiltrates the store, locates, and negotiates with him. During the negotiation, the criminal speaks of the unknown "New Order", a group of social darwinist radicals that despise modern society and believe in killing the weak, leaving only the strongest and smartest to rule the world. Cobretti then kills the gunman by throwing a knife at his abdomen and firing shots at him.
As the bodies are removed from the supermarket, Cobretti is admonished by Detective Monte (Andrew Robinson) for his seeming disregard for police procedures and protocols. Harassed by reporters, Cobretti admonishes them for failing to put the safety of potential victims first. Little does everyone realize at the time is that the supermarket hostage crisis is only one of a string of recent and seemingly unconnected acts of violence and murder that have broken loose in Los Angeles, perpetrated by the same supremacist group the supermarket gunman mentioned.
After witnessing several individuals going on a spree killing, including the New Order leader, only identified as 'The Night Slasher' (Brian Thompson), model and businesswoman Ingrid Knudsen (Brigitte Nielsen) becomes the group's main target due to her being the only living witness to their crimes. After a failed attempt on her by the group, she is placed under the protective custody of Cobretti and his partner, Sergeant Tony Gonzales (Reni Santoni). Several more attempts are made on their lives by various people connected to the Order. Cobretti theorizes that there is an entire army of killers operating with the same modus operandi rather than a lone serial killer with some associates, but his suggestion is rebuffed by his superiors. However, the LAPD agrees with Cobretti that it will be safest if he and Knudsen relocate from the city.
Cobretti becomes romantically involved with Ingrid shortly after venturing out into the countryside, but one of the Order's leaders, Nancy Stalk (Lee Garlington), a police officer escorting the Cobretti party, reveals the location of their whereabouts. Despite Cobretti's suspicions and mistrust of Nancy, he does nothing and stays the night in a motel. The Order moves in at dawn and besieges the small town. With barely enough time to react, the attackers storm Cobretti and Ingrid's motel, wounding Gonzales in the process. Killing several members but with more swarming into the town, Cobretti and Ingrid escape in a pickup truck. After the truck becomes severely damaged from the chase, the two travel on foot into a lemon grove and escape into a nearby derelict factory.
Cobretti has defeated most of the Order by this point, with the few remaining members following them into the building. After eliminating every member except for the Night Slasher himself, he and Cobretti engage in a hand-to-hand fight inside the steel mill, ending with the Night Slasher being impaled in the back by a large roaming hook and burned alive by Cobretti.
In the aftermath, Cobretti's department arrives and begins clean-up of the town, giving medical aid to Gonzales. Detective Monte (Andrew Robinson) appears apologetic but confronts Cobretti again about his lack of regard to police protocols, offering to discuss the issue over a long dinner. Cobretti punches Monte instead, and the ending credits begin as Cobretti and Ingrid climb onto one of the motorcycles left by the Order and ride away.

Question: Where did Night Slasher and Cobretti engage in hand-to-hand combat?
Answer: Steel mill