SQL server find Duplicates in column 1 while ask for 2 specific values in column 2

Question

I have a table like this:

Id  first_name  department
1   John        IT
2   George      Support
3   Jack        IT
4   Jack        IT
5   George      Dev
6   Maria       Dev
7   George      IT

I am trying to get this:

Id  first_name  department
5   George      Dev
7   George      IT

I am stuck an this:

SELECT * 
FROM tbl_employees 
WHERE first_name in ( SELECT first_name FROM tbl_employees where (department = 'IT' or department =  'Dev') 
GROUP BY first_name 
HAVING count( first_name ) > 1 )

Answer 1

SQL Fiddle

MS SQL Server 2008 Schema Setup:

Query 1:

DECLARE @TABLE TABLE(Id INT, first_name VARCHAR(20), department VARCHAR(20))
INSERT INTO @TABLE VALUES
(1   ,'John',   'IT'),
(2   ,'George', 'Support'),
(3   ,'Jack',   'IT'),
(4   ,'Jack',   'IT'),
(5   ,'George', 'Dev'),
(6   ,'Maria',  'Dev'),
(7   ,'George', 'IT'),
(8  ,'Maria',  'Support')

SELECT * FROM @TABLE 
WHERE first_name IN (
                    SELECT first_name FROM @TABLE WHERE department = 'Dev'
                    INTERSECT 
                    SELECT first_name FROM @TABLE WHERE department = 'IT'
                    )
AND department IN ('Dev', 'IT')

Results:

| ID | FIRST_NAME | DEPARTMENT |
|----|------------|------------|
|  5 |     George |        Dev |
|  7 |     George |         IT |