SQL Server 2012 :: Character Value Count From Dataset

Consider following script

create table data_set (id int primary key, col1 varchar(10))
go
insert into data_set values (1,'a'), (2,'b'),(3,'c'),(4,'d'),(5,'a'),(6,'b'),(7,'e'),(8,'f'),(9,'a'),(10,'a')
select * from data_set

I tried this below

Declare @child_ids int
@col_val varchar
@count int

select @child_ids, @col_val, @count, count(col1) as records from data_set
group by col1
order by col1

But I want my output like below .....