Song name, pls help

Hello guys. Please help me find the music video I've watched recently (but completely forgot what it was about).

I believe the music was indie and it didn't match the video, but it was very rhythmical.

The video begins with the scene in which a boy and a girl dance in the house, nd the other guy sits on the sofa nearby, then he (this guy) stands up and goes away to come back with a rapier and in a fencing mask. They laugh, and then this guy stabs a girl and beats the other guy to death.

The next scene he (person with a rapier from the previous scene) sits near the table, takes some drug (?) and goes off the house.

Then there is a mix of different situations, in which there is a man who works out and changes his appearance.

Parties, clubs, discos and the man.

The man kills the people from the parties in different places.

Somewhere near the end of the video was the scene with an African American who was having LOTS OF FUN dancing.

Please help me