The Bucks confirmed the move, and general manager Jon Horst released a statement via the team's official site:
"We believe that a fresh approach and a change in leadership are needed to continue elevating our talented team towards the next level, bringing us closer to our goal of competing for championships. Jason led a historic turnaround during his first season and would guide our team to two playoff appearances. He also played a meaningful role in helping to keep the Bucks in Milwaukee. We thank him for all of his contributions and wish him the best."
Chris Haynes of ESPN.com reported Kidd hadn't been told of the firing and that star Giannis Antetokounmpo was "devastated." On the other hand, Kidd and Jabari Parker weren't speaking, per Ryen Russillo of ESPN.
The Bucks had high expectations this season after they went 42-40 last season with a young and talented roster. But the squad is just 23-22 and stands eighth in the Eastern Conference.
Milwaukee ranks in the bottom half of the NBA in points scored (18th) and points allowed (17th) per game.
Ownership felt the team was "underachieving," according to David Aldridge of Turner Sports.
Kidd, 44, joined the Bucks in a trade from the Brooklyn Nets in 2014 but has been up and down since. He helped them to two playoff appearances in his first three years but finished with a 139-152 record in three-and-a-half seasons.
He oversaw the development of several talented young players, including Antetokounmpo, who has evolved from a raw prospect into an MVP candidate this season. Khris Middleton and Malcolm Brogdon have also exceeded expectations under Kidd.
While the squad has failed to live up to expectations in 2017-18, there is still a lot of talent between those young stars and others, such as Parker and Eric Bledsoe. Chris Herring of FiveThirtyEight described the open position:
Chris Herring @Herring_NBA
How attractive is that Milwaukee job for the time being? My goodness. Small market, but there's so much talent on that club.2018-1-22 21:04:39
In the meantime, the organization will turn to Prunty, who has never been a full-time head coach but has served on an interim basis, including for 17 games in 2015-16 when Kidd had hip surgery as well as earlier this season when Kidd left the team for the birth of his daughter.
With the top teams in the East going through slides and the rest of the conference jumbled in the standings, Prunty has a chance to find success in the second half of the season.