How do I tell my children that dad is going to jail?

I have two girls and a boy and things been hard for them this past couple weeks but something terrible has happened. Our dad went to a bar and got really drunk to the point were he got in a bar fight and hospitalized 3 people and nearly killed one of them. My kids love him to bits but I have to tell them why he was not here last night. They are all wondering were he is. What is the best way to tell them?