Mark Zuckerberg said: "our hearts go out to the friends and family" in reference to Sunday's Cleveland shooting of Robert Godwin Sr.
Steve Stephens filmed the random killing and then posted the video of the murder to Facebook. He was found dead in his car on Tuesday and is believed to have shot himself after a short police chase.
Zuckerberg said during his speech at a conference in California that the company's "next focus is to build community" and also to build "common ground" between users.
"We have a lot of work and we will keep doing all we can to prevent tragedies like this from happening," Zuckerberg said.
Facebook is also coming under fire for its management and removal of illegal and extreme content on the site. The video of Stephens' attack was live on the site for more than two hours before it was removed.
Facebook said Stephens' account was suspended within 23 minutes of the murder video being reported, but admitted it needs to "do better".
"Keeping our global community safe is an important part of our mission," the company said.