Seth Gilliam November 5 1968 is an American screen and stage actor He is most known as Father Gabriel on AMCs postapocalyptic series The Walking Dead first appearing in Season 5 He is also known for his HBO television roles first as corrections officerturnedprisoner Clayton Hughes on Oz and later as Baltimore police detective promoted to Sergeant Ellis Carver on The Wire On both of these series he costarred with Lance Reddick and JD Williams Another of his major recurring roles was on the TV series Teen Wolf as Dr Alan Deaton He had a recurring role during the seventh season of The Cosby Show as Aaron Dexter boyfriend of Erika Alexanders character Pam Law and Order Criminal Intent and Law and Order Trial by Jury Hes had a number of guest roles in other shows such as CSI Miami Nurse Jackie Skins Person of Interest The Good Wife and Bull His feature film credits include his role as Sergeant Steven Altameyer in Courage Under Fire 1996 and Private Sugar Watkins in the action movie Starship Troopers 1997 His other films include Personal Velocity 2002 Did You Hear About the Morgans 2009 and Still Alice 2014