Lucas, who grew up in Salt Lake City, didn't see or hear the gunshots but one of her colleagues witnessed a man bleeding profusely on the sidewalk outside the Transportation complex.
"We do drills. We're trained. It's not something that's completely foreign to what we think about," Lucas said Monday afternoon. "It's the nature of being in the city. ... [But] it is unnerving. I'd be lying if I said that we're not all on edge."
The Senate adjourned for the day; its buildings were locked down and staffers were told to shelter in place.
Senate Majority Leader Harry Reid said as a precaution, he didn't want the Senate to be meeting so close to the massacre.
"I urge everyone in the area to follow law-enforcement direction for their own safety, whether that means sheltering in place or simply avoiding the Navy Yard area today," Reid said.
The House Sergeant At Arms said in an email that there was no information indicating a risk to the Capitol, its staff or visitors.
Rep. Jason Chaffetz, R-Utah, who was in New York City on Monday morning, said his staff was safe but still waiting to hear details about the shooting.
"Everyone is accounted for and glued to their televisions," Chaffetz said.