The door opened into a fancily decorated bedroom. The bed was empty and there was a closed door to his right and another across the room. Sounds of gentle splashing were coming from the closed door to his right.
Theron noted the quickness to anger and intended to capitalise on it. He intentionally mumbled a response through the door that could have been 'the wargs have been shaved' for all the clarity it possessed.
Theron attuned his sight to heat in order to get a read on the man's position behind the door. Assuming he wasn't instantly spotted the thief's next moves were extraordinarily fluid. He summoned to his hand a mace of ivory, allowing the ball of the weapon to fall into his other hand, he pushed himself out from behind the door and swung the held orb at the man's head. Should he succeed in bludgeoning the man, Theron would attempt to wrap the chain of the weapon around his neck from behind and pull it tight.
When Theron switched to heat vision, he saw that his possible opponent was almost eight feet tall. Realizing that he wouldn't likely be able to reach the man's head he had to think quickly. He was still undetected for the moment.
The blow knocked that man forward, but he surprisingly scrambled away, twisting and throwing a kick at his assailant. He probably would have called for help if he wasn't currently screaming in pain. Everything was so fast the man likely wouldn't be able to describe Theron... Yet.
Theron stumbled back from the kick and swung the morningstar round in a wide arc, using the momentum to hurl the thing at the man's chest. At that very moment the light before the man's eyes scattered, depriving him a moment of his sight.
The morningstar thudded into the man's chest, his eyes widening in shock at the likely mortal wound. Theron could hear the thundering footsteps of guards on the stairs. The heat vision that he had kept active allowed him to notice that there was a ring of heat around the closed door across the room. Also from this angle he could see another door that likely led out into the hallway.
Theron quickly glanced around the room, looking to see if there were any notes or letters lying around. If his victim left something he authored around Theron might be able to convince the guards not to swarm in.
Theron started off audible and trailed off in a way he hoped would deter those who still lingered from entering. Taking a deep breath he took another look at the heat ringed door, switching to structural vision for more information.
The stone on the key flashed as he inserted it into the lock. There was a slight hissing noise as the door slid open of its own volition. Inside was a small closet. The painting he sought sat on an easel in the rear of the closet. The stone on the key began flashing steadily as soon as the door was fully open.