Police say the gunman shot and killed three people, wounding two others before killing himself.
We've heard it before: Are mass shootings on the rise?
Answering that question may depend on how you define "mass shootings," but no matter how you count them, the country is on track for a grim record this year.
President Barack Obama consoled the nation after mass shootings more than 15 times in his two terms. President Donald Trump performed those duties for the first time Wednesday and it likely won't be the last.
Wednesday's two mass shootings were the 153rd and 154th of the year, and 2017 isn't even half over. But what counts as a mass shooting?
Widely used databases define a mass shooting as four or more people shot or killed, but the FBI defines it as three or more people killed in a public place.
By the FBI's count, the San Francisco shooting is the fifth already this year. There were six last year and seven in 2015, the most ever recorded.
By the databases' broader definition, the 154 mass shootings this year, almost one per day, project to 340 by the end of the year. That would be a drop from last year's figure of 384, but it's above 2015's 334, 2014's 274 and 2013's 254.