[Python] Pandas groupby make all elements 0 if first element is 1

I have the following df:

| day | first mover |
| -------- | -------------- |
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 0 |
| 8 | 1 |


i want to group this Data frame in the order bottom to top with a frequency of 4 rows. Furthermore if first row of group is 1 make all other entries 0. Desired output:

| day | first mover |
| -------- | -------------- |
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |


The first half i have accomplished. I am confuse about how to make other entries 0 if first entry in each group is 1.

N=4
(df.iloc[::-1].groupby(np.arange(len(df))//N

Continue reading...