PHOTOS: Mass casualties in Orlando nightclub shooting
The shooting was first reported by police on Twitter just before 1 a.m. at Pulse nightclub and ended when officers fatally shot the suspected gunman, according to police.
READ MORE: Orlando mayor: 50 dead in nightclub shooting
In addition to the fatalities, 53 people were sent to the hospital, police said.
"San Francisco stands in solidarity with the community of Orlando and the nation in the aftermath of this terrible day," Lee said in the statement.
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"This is a stark reminder that violence still threatens our LGBT community. Senseless acts of violence against innocents, fueled by hate and easy access to deadly firearms, have become all-too frequent. We must continue to work each day to reduce gun violence and ensure every community is safe."
A vigil will be held this evening at 8 p.m. at Harvey Milk Plaza in San Francisco to honor and remember the victims of the shooting.
A GoFundMe account has been set up for the victims and families of the mass shooting in Orlando, click here for more information.
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RELATED: Social media reaction to tragedy in Orlando
Click here for full coverage on the deadly mass shooting in Orlando.
Profound tragedies like this leave us numb & speechless. But we resolve that love, strength & unity will triumph over hate, fear & violence.— Edwin Lee (@mayoredlee) June 12, 2016
Our prayers are with families & friends of the victims of the Orlando attack & LGBT community. pic.twitter.com/F7iMsoGBGY— Edwin Lee (@mayoredlee) June 12, 2016
FL Gov. Rick Scott: "For anybody that thinks they should do this...law enforcement will be swift in their justice." https://t.co/KarRXJELU9— ABC News (@ABC) June 12, 2016
Pulse shooting: In hail of gunfire in which suspect was killed, OPD officer was hit. Kevlar helmet saved his life. pic.twitter.com/MAb0jGi7r4— Orlando Police (@OrlandoPolice) June 12, 2016
My prayers are with the victims? families & all those affected by the shooting in Orlando. We will devote every resource available to assist— Rick Scott (@FLGovScott) June 12, 2016