Answer:
Erik's attitude when telling Mike's death to Mike's mother and talking to Arthur is the same. He talks about this death laughing, making death a joke.
Step-by-step explanation:
Erik is an extremely insensitive and psychopathic character, as he sees Mike's murder as a mere joke. He tells Mike's death to his mother and Arthur with lots of laughter. He finds Mike's younger brother's desperation at the knowledge of death very funny and spends a lot of time splitting Mike's cruel death as something fun and funny. This insensitivity of Erik, is a point very explored in "Tangerine."