nonchalantly

/ˌnɑnʃəˈlɑntli/
adverb
  1. In a calm, relaxed way that shows no worry, interest, or excitement.
    • She nonchalantly tossed her bag onto the chair and sat down.
    • They nonchalantly walked past the crowd as if nothing had happened.
    • He nonchalantly answered the phone while the alarm was ringing.