WASHINGTON — WikiLeaks has offered a $20,000 reward for information leading to the conviction of the killer of a Jewish Democratic Party staffer.The offer from the clearinghouse for hacked and leaked documents was made Tuesday on Twitter, but it came after Roger Stone, a onetime adviser to Republican nominee Donald Trump, alleged on Twitter that Hillary Clinton was responsible for Seth Rich’s death.Rich, 27, from Nebraska, had worked at the Democratic National Committee on a database to expand voter registration.He was shot dead in what Washington D.C. police have said was possibly a botched robbery while he was walking home before dawn on July 10.Stone said Rich was on his way to meet with the FBI. Stone provided no evidence for his claim.Julian Assange in an interview on Netherlands TV suggested that Rich might have been a source for the leaks clearinghouse.“We are investigating what happened with Seth Rich. We think it is a concerning situation,” Assange said in comments posted by Buzzfeed. “There is not a conclusion yet; we are not willing to state a conclusion, but we are concerned about it. And more importantly, a variety of WikiLeaks sources are concerned when that kind of thing happens.”Assange would not say outright if Rich was a source, at one point saying “others have suggested” that Rich was murdered.Stone said in a speech on Monday he was in touch with WikiLeaks founder Julian Assange about releasing documents that could damage the Clinton campaign.WikiLeaks last month released Democratic National Committee emails that revealed antagonism among the DNC leadership toward Bernie Sanders, who earlier in the month had conceded the nomination to Clinton. The revelations led to the resignation of top DNC staff members.US authorities have said it is likely the emails were the result of a hack originating in Russia. No one has alleged involvement of a DNC staffer.Democrats and Clinton have said they believed the Russian government was involved in the hacking, and Clinton’s defenders on social media have alleged that Assange has worked in cahoots with the Russians. Wikileaks and Assange have in recent days repeatedly attacked Clinton and the DNC.Stone, in the same tweet, blamed Clinton for the death on Aug. 1 of Victor Thorn, a writer who, like Stone, engaged in conspiracy theories focused on the Clintons. Thorn also peddled Holocaust denial. His death was ruled a suicide.