In a dramatic blow-by-blow account, Representative Mo Brooks of Alabama told CNN the gunman was armed with a rifle and appeared to be a white male, "a little bit on the chubby side."
Brooks said he saw the man only for a second, and that he was shooting from a chain link fence behind the third base position on the field where the congressional group was holding its morning practice.
"There must have been 50 to 100 shots fired," he told CNN. "I hear Steve Scalise over near second base scream. He was shot," said Brooks, adding he helped apply a tourniquet with his belt to a congressional staffer who was shot in the leg.
Fox News anchor Bret Baier tweeted that Scalise was shot in the hip and is expected to survive.
US President Donald Trump, a Republican, said he and Vice President Mike Pence were aware of the shooting and are monitoring developments closely.
"We are deeply saddened by this tragedy. Our thoughts and prayers are with the members of Congress, their staffs, Capitol Police, first responders, and all others affected," Trump said in a statement.
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