Watch the latest video at &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;a href="//video.foxnews.com"&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;video.foxnews.com&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/a&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;

Authorities in Cleveland have intensified their search for a man suspected of killing an elderly man while broadcasting live on Facebook over the weekend.

Cleveland Mayor Frank Jackson announced a $50,000 reward on Monday afternoon in what Cleveland police chief Calvin Williams said is now a “national search.”

Police issued a warrant early Monday morning for the arrest of 37-year-old Steve Stephens, according to reports, who has been charged with the aggravated murder of 75-year-old Robert Godwin Sr.

Stephens has not been spotted since the Sunday afternoon shooting in Cleveland, which he broadcast live on Facebook.

“At this point he could be a lot of places," said Steve Anthony, the special agent in charge of the FBI's Cleveland division. "He could be nearby, he could be far away or anywhere in-between.”

Police are searching for the suspect in Pennsylvania, New York, Indiana and Michigan, and have warned residents to be on alert.

“I think we can say, without a doubt, he’s armed,” Williams said.

Williams said earlier Monday that one of his detectives had spoken with Stephens over the phone and attempted to get Stephens to surrender, but did not include further details.

ADVERTISEMENT

"We're still asking Steve to turn himself in, but if he doesn't, we'll find him," Williams said. "We're not going to stop until we find him."

Several schools in Philadelphia were briefly locked down after reports that Stephens might have been spotted in the area, according to a local ABC affiliate.

Pennsylvania authorities also reported earlier that Stephens's cellphone emitted a signal in Erie, Pa.

But Philadelphia Police later said that there was “no indication that the subject is at that location, or anywhere in the city of Philadelphia."

Statement on police activity in Fairmount Park regarding Cleveland Ohio homicide suspect Steve Stephens pic.twitter.com/qYkd2DzxbP — Philadelphia Police (@PhillyPolice) April 17, 2017

Stephens is now on the FBI's 10 Most Wanted List, USA Today reported.

Facebook responded Sunday afternoon.

“This is a horrific crime and we do not allow this kind of content on Facebook,” a Facebook spokeswoman said in a statement, according to CNN.

“We work hard to keep a safe environment on Facebook, and are in touch with law enforcement in emergencies when there are direct threats to physical safety.”

The Facebook video of the shooting remained on the platform for nearly three hours before it was removed, according to Cleveland.com. Stephens’s personal profile has also been deactivated.