This is Sean Whent's resignation letter- sent via email last night at 9:17 pm. #abc7now pic.twitter.com/qKWpGgKbPB — Tiffany Wilson (@TWilsonTV) June 10, 2016

Whent: having made much progress in OPD over past three years (homicide/shootings down by 39%) "I believe timing is good for me to move on" — Tiffany Wilson (@TWilsonTV) June 10, 2016

Whent thanked city leaders for the opportunity, says it was an honor to work with and lead OPD over last three years. — Tiffany Wilson (@TWilsonTV) June 10, 2016

OAKLAND, Calif. (KGO) -- One Oakland city leader has gone on the record saying he thinks the city's police chief was forced out.Sean Whent emailed his resignation to the mayor Thursday night. BART deputy chief Ben Fairow will take over as interim chief.The city released Chief Sean Whent's resignation letter today and it doesn't give a reason for his departure, just that violent crime is down 40 percent and it's time to look for other opportunities. But others think it goes deeper than that."Last night we received the resignation of our police Chief Sean Whent, effective today," said Oakland's Mayor Libby Schaaf.That's how Schaaf announced Friday that Oakland was losing another police chief, it's the third in five years.Exactly why Whent is leaving isn't completely clear. The city made his resignation letter public Friday. In it Whent took credit for a 39 percent drop in violent crime, but as to reasons, he would only say quote "having made so much progress on what I intended to do when I took over, I believe the timing is good for me to move on and to explore other opportunities.Oakland city councilman Noel Gallo says he was shocked to find out the chief was leaving last night. He believes all signs point to a man being forced out.The big unanswered question is whether Whent's resignation was at all related to a sex scandal allegedly involving several OPD officers and the young daughter of a police dispatcher."I think it's very important to be clear that the chief has never been a subject of the investigation of sexual misconduct in this department," Schaaf said.Not a subject, but it happened on his watch. Gallo says he may be taking the hit for it."They're supposed to be the ultimate role model when it comes to following the law," Gallo said."I think him leaving in that way, in that fashion, I think other folks had a lot to do with him leaving," Gallo said.Mayor Schaaf says she will launch a nationwide search for a replacement. In the meantime, former Oakland police Capt. Ben Fairow, now a Deputy chief at BART - will be acting Oakland Chief. And he promises to continue to reform the department and continue crime reduction plans that work.One councilman says he has his work cut out."Crime is at its lowest in the city of Oakland and it made no sense to me or my colleagues that I talked to last night that the chief would resign," said Oakland city council member Larry Reid.