Creating two new columns and removing the source column

I have the following example data:

df <- data.frame(ID=c("A1","A2","A3","A4","A1","A2","A3","A4"),
                 NUM=c(469,586,394,595,398,203,604,809))

I am looking to extract the first value of the NUM column and place it in a new column NUM1, and then on the second occurrence of a NUM value for the same ID, extract that value into a new column NUM2. Finally, I would like to remove the original column. The dataset I have has many more variables and columns in addition to ID and NUM. The following is the desired output.

df1 <- data.frame(ID=c("A1","A2","A3","A4"),NUM1=c(469,586,394,595),NUM2=c(398,203,604,809))