LAS VEGAS -- The American Red Cross is pleading for blood donations after the largest mass shooting in modern history.

The organization is already on the ground helping victims after a man opened fire from above a music festival in Las Vegas overnight. The shooting left more than 50 people dead and hundreds injured. Among the dead and injured were on-duty police officers.

The Red Cross said it had already provided more than 250 additional blood products to hospitals to help those who were injured and that they will continue to help as needed.

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However, this senseless tragedy has also left the organization in need of more blood donations to resupply.

"Last night’s tragedy illustrates that it’s the blood already on the shelves that helps during an emergency," the Red Cross said in a written statement. "Red Cross blood donations will become part of our national blood inventory, helping to ensure we are prepared for any blood needs that arise wherever blood is needed."

Those eligible can make an appointment to give blood in the coming weeks and months by using the Red Cross Blood Donor App, visiting RedCrossBlood.org, or calling 1-800-RED-CROSS.

Meanwhile, the Red Cross is also providing "mental health and spiritual care" to those family members coming to terms with the tragedy.

"The thoughts and deepest sympathies of the entire American Red Cross family are with all those affected by Sunday night’s tragic shooting in Las Vegas," the organization said.