How is tension created through thriller?

The scene opens with a close up image of a man with his eyes wide open. This alarming image  immediately makes the audience feel on edge and shows that the sequence is based around this man.

Throughout the sequence there is a muffled sound of an argument between a man and a women. As the arguing becomes louder and more aggressive the tension rises. This is because you can hear the action but you cannot see it. Your imagination then creates the worse scenario. In this situation, my mind went straight to the man involving violence or enforcing abuse. 

Whilst the couple are arguing, the man is completely unaffected by it and continues with his routine in his eery flat. This numb reaction means that he is either used to hearing the sounds of abuse and aggression and possibly violence, or he feels he has no obligation to help people in need. This suggests that the man doesn't feel ordinary human emotions, and is possibly scarred from previous experiences. These characteristics add to the tension building. 

Whilst the man walks around his flat, hip hop music runs over the sound of the argument. This genre of music adds danger and unease to the atmosphere. Sirens are also heard, suggesting crimes or fatalities. This, along with the thin walls (an assumption made from the argument clearly heard from the neighbouring flat) suggests he lives in an unprivileged area, where crime is the norm, perhaps a council estate. 

As the man pulls the gun from under his table, it is almost an anticlimax, as he does it in such a relaxed fashion. This implies that this is a normal routine and he is very used to handling such dangerous equipment. When he first lifts the gun, the camera films this from a low angle looking up at him. This angle perceives him to be massive and he becomes very threatening to the audience. He then cocks the gun, and looks down the scope. The camera zooms in on him at this point and demonstrates a frontwards angle. This is a tense moment as the gun is pointed straight at the camera, making the audience feel scared.

He then puts the gun in an oversized sports bag, (a very casual way to hold such a lethal weapon) 

puts a beanie hat over his head, and pulls his hood up. The manor in which he prepares to leave the house shows he has done this before, almost as if it is a routine. The way he hides his face with a hood, shows he doesn't want to be recognised and suggests he is going to commit a serious crime. This builds tension in many ways as the audience wonder what he is going to do. He grabs his bag and walks out the flat with purpose, leaving the audience in great suspense.