Following a showdown on Southend Pier, Ryan will kill Rob Grayson (Jody Latham) as revenge for forcing his sister into prostitution.
Ryan, played by Neil McDermott, will say his goodbyes to Whitney (Shona McGarty) before disappearing into the crowd and going on the run from police.
"Ryan's been involved in some big storylines so we wanted him to leave in typically dramatic fashion," a source told the News of the World.
"Neil felt it was time for him to spend more time with his family. However, he has not been killed off, so there is always a chance he could return in the future."
McDermott announced he was quitting the BBC One soap last week.