During his attempt to defect to the Federation in 2375, Weyoun 6 activated his termination implant in order to force the Jem'Hadar away from the USS Rio Grande, the runabout he was aboard with Odo. (DS9: "Treachery, Faith and the Great River") Presumably Yelgrun had a termination implant as well, but for some reason decided not to activate it. It was known that Keevan chose not to commit suicide.