Police said they have received "dozens and dozens" of tips about the possible location of the suspect, Steve Stephens, and tried to convince him to turn himself in when they spoke with him on his cellphone on Sunday after the shooting. But Stephens remains on the run as the hunt for him expanded nationwide, police said.
The shooting is the latest violent incident shown on Facebook, raising questions about how the world's biggest social media network moderates content.
"Our reach now is basically all over this country," Cleveland Chief of Police Calvin Williams told a news conference in Cleveland. "This is what we would consider a national search."
A reward of $50,000 was being offered for information regarding Stephens' location, officials said.
Police said Stephens used Facebook Inc's <FB.O> service to post video of him killing Robert Godwin Sr., 74. Stephens is not believed to have known Godwin, a retired foundry worker who media reports said spent Easter Sunday morning with his son and daughter-in-law before he was killed.
Godwin was the father of nine children and grandfather of 14, his son, Robert Godwin Jr., told the Cleveland Plain Dealer. Godwin Jr. could not immediately be reached by Reuters to comment.
Stephens mentioned a former girlfriend, Joy Lane, before shooting Godwin.
"I am sorry that all of this has happened," Lane told CBS News in a text message. "He was kind and loving to me and my children. This is a very difficult time for me and my family."
Reuters was not able to reach Lane by phone or email for comment.
Stephens, who has no prior criminal record, is not suspected in any other murders, despite a claim he made in the video of having killed more than a dozen other people, police said.
"To be honest, we've interviewed several people involved in this and I don't think there is any rhyme or reason for it happening," Williams said.
The last confirmed sighting of Stephens was at the scene of the homicide. Police said he might be driving a white or cream-coloured Ford Fusion, and asked anyone who spots him or his car to call police or a special FBI hotline (800-CALLFBI).
Stephens had worked since 2008 as a vocational specialist and youth mentor at Beech Brook, a behavioural health agency located outside Cleveland. Beech Brook's offices were closed on Monday.