Let Xak, BP and I's powers combine and summon Captain Bullshit. With muscles and everything.
The culprit is X.
The night before, Wolfgang forgot to lock the door to his apartment after returning home. The culprit or Beowulf went into the apartment, did something (like get the knife) and left, leaving behind a trail of blood. The trail of blood could've been left due to Beowulf's actual injury if it was him, or by the blood culprit got on him while treating the injury.
Alternatively: Wolfgang slept with his window open and the culprit snuck in, leaving through the door.
If the door was locked when Wolfgang woke up, the culprit locked it by simply setting the deadbolt on before leaving, causing it to lock behind him when he shut the door.
Alternatively: Culprit entered through the unlocked door, locked it behind him, did his thing and left through the open window.
The intruder doesn't notice the trail of blood due to the darkness. Wolfgang doesn't notice the trail of blood the next morning because he's in a rush. The other tenants don't notice the trail of blood because they don't step out into the hallway to begin with -- they're in self-isolation.
For the ferris wheel escape: X puts a cardboard cutout against the window of a cabin 3 cabins or so away from Beowulf's. It is outside of the cabin, not contradicting the red. Beowulf gets locked in, then Wolfgang enters the booth and looses sight of Beowulf. Beowulf ducks, so all wolfgang see is the cutout. The cutout is brought to the top.
When the ferris wheel is brought down, the wrong cabin is there. Meanwhile, the cabin Beowulf is actually in is positioned directly above the control booth. The culprit opens the lock and lets Beowulf escape. While getting off the top of the booth, Beowulf's leg wound reopens.
The cutout itself disappears either due to a string pull, or by falling off on its own at some point due to the wind.
The culprit and Beowulf go to the apartment building. They enter through one of the upstairs windows, avoiding the camera.
The culprit treats Beowulf's wound. While doing this, he plants a bag of cyanide to burst and kill Beowulf instantly.
11 PM. Wolfgang returns. Beowulf sees the goons decend upon the place. Thinking X betrayed him, Beowulf and X fight. X stabs Beowulf in the back with the kitchen knife from Wolfgang's apartment, but it doesn't go in deep enough to kill him.
Beowulf runs downstairs. Just as Wolfgang's attention's drawn away from the door because of Fenris, Beowulf goes into the apartment, setting the chain and leaning against the door.
At this moment, the bag of cyanide bursts, killing him instantly.
When Fenris devours the door, he sends Beowulf's body flying across the door. The force of the impact also causes the knife to wedge itself deeper, making it appear as if it was the cause of death.