Sunday morning’s tragic shooting at Pulse, a gay nightclub in Orlando, Florida, is the worst mass shooting in US history, leaving at least 50 people dead and 53 more injured.

OneBlood, a blood donation organization in Florida, reported an urgent need for O-negative, O-positive and AB plasma blood donors.

"Blood is a wonderful gift," said Orlando Health surgeon Dr. Michael L. Cheatham said at a press conference, urging potential donors to head to local blood banks, which would be more useful than trying to donate at the hospital itself.

In most cases, most gay and bisexual men and transgender women would be barred from helping their own community. Some are reporting that OneBlood is accepting donations from anyone who is willing to give blood, and then screening later. Vox has not independently confirmed this to be true. OneBlood tweeted Sunday that the FDA blood ban is still intact, but not did clarify whether the center is accepting donations regardless of sexual orientation or gender identity.

All FDA guidelines remain in effect for blood donation. There are false reports circulating that FDA rules were being lifted. Not true. — OneBlood (@my1blood) June 12, 2016

Still, before this distinction was made Sunday morning, the irony was not lost on some, including my former colleague Slade Sohmer, and the ACLU’s Chase Strangio:

Only thing I'd add to saddest tragedy in Orlando: It's made even more tragic and sad that gay men are prohibited from donating blood to help — Slade Sohmer (@Slade) June 12, 2016

But not if you're gay or trans. Then you're banned from saving your community. https://t.co/AQpPDHiIpI — Chase Strangio (@chasestrangio) June 12, 2016

In 2015, the US Food and Drug Administration lifted its three-decade lifetime ban on all men who have ever had sex with men, as well as transgender women, from donating blood.

The ban, however, wasn’t completely lifted: Instead of the lifetime ban, it now stands for men who have had sex with another man in the previous year. This classification is also applied to transgender women, which has been a distinct fight all its own.

Women who have sex with a man who has had sex with another man in the last year are also banned from donating.

Why was there a ban in the first place?

The rationale in 1983 when the ban was enacted was to prevent the spread of HIV/AIDS through blood transfusions. Then, gay and bisexual men were overwhelmingly tied to the epidemic. Later, of course, testing for HIV has drastically improved, and it’s now understood that HIV is not limited to men who have sex with men. But the ban remained, amid years of activism from those who saw the lifetime blood ban as discriminatory.

Even the nation’s biggest blood banks, the American Red Cross and America’s Blood Centers, have called the bans "medically and scientifically unwarranted."

When the ban was dialed back last year, Vox’s Julia Beluz explained the one-year ban still seems arbitrary, and it doesn’t really address its discriminatory nature, since gay and bi men as well as transgender women in monogamous, sexually active relationships are also barred from donating.

"There are irrational aspects of the policy," said Sean Cahill, director of health policy research at the Fenway Institute last year. "If you are a heterosexual man who admits to having unprotected sex with a sex worker or prostitute, you can wait one year and donate blood. But a gay man who has been in a monogamous relationship and who tests negative for HIV still can't."

Meanwhile, before the ban was changed last year, the Williams Institute, an LGBTQ think tank at the University of California, Los Angeles, said lifting the ban completely would increase the national blood supply by as many as 615,300 additional pints of blood each year, and possibly save about a million lives per year.

The Pulse shooting will undoubtedly leave a scar on the local LGBTQ community, and the federal blood ban prevents some in the community from helping supply a vital resource we all have: our blood.