He was hired just eight days later on June 14th by the Vegas Golden Knights to be their third head coach is franchise history.
It appears that the club has taken a very large liking to their new coach, including a somewhat weird preseason gift in Cassidy's honour.
As per the Golden Knights Twitter:
Bruce Cassidy was successful as the Bruins head coach. He appeared in 399 games behind the bench, with a record of 245-108-46.
He also got the club to the playoffs in all six years he was here and finished with an overall record of 36-37. Losing in the Stanley Cup Final to the St. Louis Blues in 2019.