after six city officers charged in the murder of freddie gray. 25-year-old gray was badly injured during an arrest last month and died one week later. ari melber with a welcome to you, when you look at investigation of this type what does it entail? >> thsz a pattern and practice investigation that operates under the 1994 criminal act and what it basically says is that the justice department can go in and look top to bottom at how a police department is functioning and what are the policies in place and what are the num erical quote tas all the way down to what the police are doing. they've done this in over 20 different police departments. baltimore is a big one and as the attorney general said today, in response to the outcry over the freddie gray case. >> we heard this famously happened in ferguson and it can result with really positive change. what can possibly happen here with baltimore? >> it can be very positive.