If you're a man who has sex with men in the USA, you can't donate unless you've abstained from sex for a year.
People are also being encouraged to donate to the American Red Cross, which accepts donations on its website, by phone in the U.S. at 702-369-3674 or via mail at 1771 East Flamingo Road, #206B, Las Vegas, Nevada, 89119.
"There is no guarantee this is going to help someone in Las Vegas but people are people everywhere so if it will help somebody here, that's cool", said Dave Lucitt, another donor. Green says they are all safe. "So, just kind of grief whether you were there or knew someone or not".
They wrote: "Wanting to donate blood since I'm considered the universal donor but can't since I'm gay wow this is bull****".
She was one of the first through the doors.
"We're kind of standing by ready to help if asked", Baker said.
People are also helping victims of the tragedy and their families by giving money to the National Compassion Fund and donating blood to participating hospitals and clinics.
Vincent Sayles gave back, too.
"People need. Gotta provide".
"I can imagine that there will be specific drives to help with the aid for patients but one of the good things this does is raise awareness", Reid said.
Residents in Santa Clarita can also donate blood through the organizations to help free up the overall blood supply and to assist Las Vegas hospital in the event of a blood shortage.
"It is very important and of course it is always needed".