"A question people ask because it's something that less that 1% of our American population will ever experience. Especially one on a daily basis. My response has always been the same, not one filled with a sense of pride or ego, but an answer filled with truth and genuine fear/anger. *which by the way, go hand in hand*," he posted.
It is understood he was in Las Vegas with his mother Debby Allen.
After the shooting she posted a series of frantic messages on Facebook.
"I am safe. I just can't find Christopher Roybal anywhere. He's not answering anyone's phone calls," her first message said.
"God help me," she later wrote.
Her second post read: "update, my baby Christopher Roybal was shot and is still "missing".
Four hours ago she posted a photograph of Roybal.
Earl Marsh posted a photograph of Roybal in his army uniform soon after.
"Chris Roybal died last night in Las Vegas," Marsh wrote.
"As you can see he served in the 25th and 4th Infantry Divisions in Afghanistan... Sad he honourably served his country against a foreign enemy only to be shot.
"Sad he honourably served his country against a foreign enemy only to be shot down by a coward back here in the USA... RIP Chris... I never knew you but proud to have served in the same military as you..."
Tribute messages are now pouring in on Roybal's page.
A fundraising page has been set up to help his family with funeral costs.
