CLEVELAND, Ohio -- Authorities on the hunt for a suspect who they say fatally shot an elderly Cleveland man in a gruesome video posted on Facebook say his last known location was at the shooting site.

Police and the FBI in Cleveland said Monday that the suspect, 37-year-old Steve Stephens, could still be in the city or in surrounding states.

A reward of up to $50,000 is being offered leading to his arrest. 

Chief Calvin Williams says detectives talked with Stephens by cellphone Sunday after he shot 74-year-old Robert Godwin Sr. but haven't had contact since.

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Authorities are telling people in Pennsylvania, New York, Indiana and Michigan to be on the lookout. They say Stephens should be considered armed and dangerous.

Cleveland's police chief says officers have searched dozens of places since the shooting Sunday and told residents to go about their business, but be careful.

Around midnight, police tweeted that an aggravated murder warrant had been issued for the suspect.

Stephens, a 6-foot 1-inch African-American man, said on Facebook that he had committed an "Easter day slaughter." Police late Sunday said they couldn't identify other homicide victims but "continue to search multiple areas."

Stephens was reported to be driving a light-colored Ford Fusion. Police called him armed and dangerous. He was last seen wearing a dark blue and gray or black striped polo shirt.

Photos: Steve Stephens - man wanted in Facebook killing

Police identified the victim as Robert Goodwin Sr., 74.

In the video, which appears shaky, Stephens gets out of his car and appears to randomly target Goodwin, who was walking on a sidewalk carrying a shopping bag. Stephens says the name of a woman, whom Goodwin does not seem to recognize.

“She’s the reason that this is about to happen to you,” Stephens told Goodwin before pointing a gun at him. Goodwin can be seen shielding his face with the shopping bag.

Cleveland Mayor Frank Jackson publicly urged Stephens to turn himself in to police and not to “do any more harm to anybody.”

“Any problems he is having, we can have a conversation,” Jackson said.

Authorities on Sunday said a series of posts on Stephens' Facebook page complained that he had "lost everything" to gambling, NBC News reported. Stephens allegedly wrote: "I killed 12 people today," and said he wouldn't stop until he could speak to his mother and a second woman.

Later, the user posted: "I killed 15 today because of [the second woman]," but police said no other victims had been found. The video of the killing remained on Facebook for nearly three hours before it was taken down and Stephens' page deactivated, The (Cleveland) Plain Dealer reported.

Stephens was a counselor for Beech Brook, a children's behavioral health agency.

"We were shocked and horrified yesterday to learn about the situation involving the threats by Steve Stephens and the tragic shooting of Mr. Godwin," the organization posted on Facebook. "Our hearts go out to his family during this time of grief."

Beech Brook said its offices were closed Monday "out of concerns for the safety of our staff, clients and other visitors to our sites."

Facebook issued a statement calling the shooting "a horrific crime," adding: "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.”

Several recent shootings have played out live on the online platform, including the police killing last July of Philando Castile during a traffic stop. Also last July, three people were injured in a shooting captured on Facebook Live in Norfolk, Va. The men were sitting in a car listening to music when the shooting took place. The phone streaming the shooting fell to the floor of the car and continued recording for about two hours as police arrived and bystanders offered aid.

Contributing: The Associated Press. Follow Greg Toppo on Twitter: @gtoppo