DB Query matching ids and sum data on columns

Here is the info i have on my tables, what i need is to create a report based on certain dates and make a sum of every stock movement of the same id

Table one                   Table Two
  Items                        Stocks
----------           ---------------------------
ID  - NAME           items_id  - altas - bajas - created_at

1     White             4          5       0         8/10/2016
2     Black             2          1       5         8/10/2016
3     Red               3          3       2         8/11/2016
4     Blue              4          1       4         8/11/2016
                        2          10      2         8/12/2016

So based on a customer choice of dates (on this case lets say it selects all the data available on the table), i need to group them by items_id and then SUM all altas, and all bajas for that items_id, having the following at the end:

items_id   altas  bajas  
  1         0      0
  2         11     7
  3         3      2
  4         6      4

Any help solving this?