Use the past progressive tense to talk about actions that were going on at a certain moment in the past.
Miss May was cleaning the chalkboard.
Sally was packing her books into her schoolbag.
Jenny and I were tidying the classroom.
The twins were fighting in the corner.
Michael and John were washing the paint brushes.
Mom was cooking our supper when I came home.
Kaynak: Basic English Grammer Book1