SAN FRANCISCO (AP) — A Reuters deputy social media editor accused of conspiring with hackers to deface a Los Angeles Times story said Monday he had been fired.

His dismissal came the day before 26-year-old Matthew Keys was scheduled to appear in federal court for the first time on the felony charges. His attorneys say he plans to plead not guilty.

Federal prosecutors allege Keys provided the hacking group Anonymous with login information to access the computer system of The Tribune Co., the Times' parent company.

According to a federal indictment handed down last month, a hacker identified only as "Sharpie" used information Keys supplied in an Internet chat room to alter a headline on a December 2010 Times story to reference another hacking group.

Tribune also owns a Sacramento television station Keys had been fired from months earlier.

Keys has said he did not commit the crimes he's accused of. He did not immediately respond to a telephone message seeking comment Monday, but he did post several online messages saying Reuters had not fired him as a result of the indictment.

"Just got off the phone. Reuters has fired me, effective today. Our union will be filing a grievance. More soon," he tweeted to his more than 35,000 followers.

He later tweeted a copy of a "final written warning" he said he received from Reuters in October, which admonished Keys for mocking a Google executive from a fake Twitter account he had created, saying the action demonstrated a "serious lapse of judgment and professionalism that is unbecoming of a Reuters journalist."

His attorney Jay Leiderman confirmed the firing, but said he would not comment on it because the Newspaper Guild was representing him on the matter. He added that "there is an appeals process that I will have to let play out."

Peter Szekely, Secretary-Treasurer of the Newspaper Guild of New York, confirmed the union would be representing Keys.

"Our contract with Thomson Reuters prohibits management from dismissing anyone without just and sufficient cause. We don't believe the company has the required justification here," Szekely said in a statement. "At this point, we intend to vigorously defend Matthew Keys as we would any other hard-working member of the Newspaper Guild of New York who had been fired without cause."

Reuters hired Keys in 2012 and suspended him from his New York social media job March 14. Thomson Reuters spokesman David Girardin declined to elaborate Monday on why Keys was no longer employed.

Keys is scheduled to be arraigned Tuesday in federal court in Sacramento. He is charged with one count each of conspiracy to transmit information to damage a protected computer, as well as transmitting and attempting to transmit that information.

If convicted and sentenced to the maximum for each count, the Secaucus, N.J., resident faces a combined 25 years prison and a $500,000 fine, prosecutors say. However, experts say first-time offenders with no criminal history typically spend much less time in prison than the maximum term.

___

Follow Garance Burke at http://twitter.com/garanceburke.