The search for 37-year-old Steve Stephens – dubbed the “Facebook killer” by some – is now a national manhunt, Cleveland police said Monday evening. Stephens got his moniker because he posted a video on Facebook which depicted him pulling a gun and shooting and killing 74-year-old Robert Godwin on Sunday.

Philadelphia police said schools in the area were put on lockdown Monday afternoon while authorities investigated reported sightings of Stephens. Authorities also said that there had been no evidence that Stephens was in the Philadelphia area.

Cleveland police are offering a $50,000 reward for information related to Stephens and authorities say to contact police if he’s spotted. So far, officials said, they have received “dozens and dozens” of tips related to Stephens from Facebook users.

Police said Monday morning Stephens “may be out of state at this time,” and could be in Ohio, Pennsylvania, New York, Indiana, or Michigan. The search had expanded beyond those states by the evening. Officials said residents should stay on alert for the suspect and Cleveland police chief Calvin Williams told reporters that Stephens “is considered armed and dangerous,” adding that the situation had been “traumatizing” for the community.

News of the murder went viral on Sunday, after Stephens posted a video on Facebook that showed the act, which Stephens allegedly committed after Godwin had enjoyed an Easter meal with his children.

In the horrific video, which authorities confirmed was legitimate, Stephens could be heard driving down the road and saying, "Found me somebody I'm going to kill, this guy right here, this old dude." Stephens then exited the car and approached Godwin.

He asked Godwin how old he was before pulling out a gun and pointing it at Godwin's head. Godwin could be seen attempting to shield himself before Stephens fired the gun, killing Godwin. He then walked back to his car and drove off.

Stephens and Godwin did not appear to know each other, according to authorities.

"From what we can tell now, it's just a random person that he picked out. We don't know why," Williams, the police chief, said.

Stephens' mother told CNN that when she last saw him on Saturday, he told her that it would be "a miracle" if she ever saw him again. She added that when they spoke the next day, he told her that he was killing people because he was angry at his girlfriend. In another video Stephens recorded, he claimed to have murdered 13 people and said he was going to kill more.

"I snapped … I just snapped ... I killed 13 people, and I'm about to keep killing until … until they catch me, f--- it," Stephens said on the phone, speaking to a friend or family member. He could also be heard encouraging the person on the other end to watch the video of the murder he'd uploaded on Facebook.

Facebook took the video down after multiple people reported it, though it took the tech giant three hours to do so, garnering criticism from some. Facebook has received ridicule in the past for graphic content that users have posted to the site, such as a beating video streamed on Facebook Live in January.

"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," a company spokesperson said in a statement on Sunday.

Williams told reporters Monday morning that Stephens has a number of motor vehicle and traffic violations but no criminal record. Stephens was last seen wearing a dark blue and gray or black striped polo shirt. He was driving a white Ford Fusion with temporary license plates, Cleveland police said.