EMBED >More News Videos The Harris County Sheriff's office says they've terminated a deputy who had a relationship with Deputy Darren Goforth's mistress.

EMBED >More News Videos Neighbors are shocked that Deputy Marc DeLeon was fired for his relationship with the mistress of slain Deputy Darren Goforth.

HOUSTON (KTRK) -- A third law enforcement official is now under investigation for allegedly having a relationship with the mistress of Deputy Darren Goforth, the officer who was fatally shot at a gas station in northwest Harris County last year. The news comes on the same day the Harris County Sheriff's Office announced the termination of the second deputy who had a relationship with the same woman.The newest development also could affect the ongoing capital murder case against Shannon Miles, the man accused of gunning down Goforth on August 28.Harris County Sheriff Ron Hickman says the third officer is still on the job as the latest internal affairs investigation continues, but he anticipates some kind of disciplinary action will be taken against that employee, too."This seems to be a never-ending cycle of conduct that's embarrassing to every professional peace officer," Hickman said. "We'll continue doing what we're doing: to make sure that we point out and respond to allegations of improper conduct, that we respond correctly and proportionately and that we do what we can to make sure that our agency has the public's trust that those issues will be rooted out and handled."Earlier Wednesday, HCSO announced the termination of Deputy Marc DeLeon for his relationship with the same mistress. Officials say DeLeon wasn't fired because of the relationship, but for trying to withhold that information from others."This particular deputy knew the witness before the incident ever even occurred," Miles' defense attorney, Anthony Osso, said.Sources say Deputy DeLeon responded to the Goforth murder scene that night. The Harris County Sheriff's Office is looking into what role he played in the murder investigation.DeLeon isn't the sheriff's office employee terminated for his relationship with Goforth's mistress. In October, Sgt. Craig Clopton was fired after he admitted to engaging in consensual sexual conduct with the same woman."Any law enforcement leader would say that we are disappointed in an event that colors our reputation in the community poorly," Hickman said following DeLeon's termination.The HCSO says it is in the early stages of the investigation against DeLeon. The deputy can appeal the decision, which his attorney indicated he might do in a statement issued Wednesday afternoon:"Mr. De Leon has no comment as to the facts surrounding his separation of employment from the Harris County Sheriff's Office, at this time, as he will avail himself of the appeal process under Harris County Civil Service Rules."DeLeon's neighbors are shocked."I'm really surprised and kind of saddened by this because I know Marc. He's a really nice guy, he's really helpful. My son looks up to him. So, I feel really bad about the whole situation," one neighbor told Eyewitness News.