Police late Sunday said they couldn't identify other homicide victims but "continue to search multiple areas".
Steve Stephens, 37, is now harder to track as a result, the sources told cleveland.com Sunday night.
Police said late Sunday that Stephens "may be out of state at this time", and authorities called on residents of Pennsylvania, New York, Indiana and MI "to be on alert".
Then in March, a 15-year-old Chicago girl was apparently sexually assaulted by five or six men or boys on Facebook Live, and none of the roughly 40 people who watched the live video reported the attack to police, authorities said.
Facebook allows any user to live-stream video from their phones, a service started in 2010.
This story has been corrected to show the name of the victim is Robert Godwin Sr., not Goodwin.
"Like I said, I killed 13, so I'm working on 14 as we speak", he said.
Kortemeyer says she hopes that Steve Stephens is "arrested as soon as possible" and that no one else is harmed. What happened in Cleveland on Sunday?
According to its website, Beech Brook says it will serve more than 18,000 children and families in northeast OH this year.
Facebook has released a statement condemning the killing of a Cleveland man that police say was posted on the social media site. He is considered armed and unsafe.
After announcing that he meant to kill a random person, he exited his vehicle and approached 74-year-old Robert Goodwin, who was walking down the sidewalk at the time.
Stephens approached Godwin as the elder man walked along the sidewalk and asked him to repeat the name of Stephens' girlfriend before shooting Godwin, the video shows.
Mayor Frank Jackson told reporters police were still trying to communicate with the suspect.
The suspect said in a separate video he has also killed more than a dozen other people.
Police have not verified this, said spokeswoman Sgt. Jennifer Ciaccia. If seen call 9-1-1.
Stephens was reported to be driving a light-colored SUV.
"He needs to turn himself in so that he can get the help that he needs and he can't keep victimizing this community based on his issues", Williams said.
"We were shocked and horrified to learn of this news today", Kortemeyer said in a statement to FOX 8. And in 2015, a shooter killed a TV journalist and her cameraman during a live-TV broadcast before posting his own video of the killing on Facebook. His Facebook page apparently was deactivated later Sunday afternoon.
"Suspect in this case is. armed and unsafe".