WASHINGTON - Sen. Tom Carper, chairman of the Homeland Security Committee, said today that the Navy Yard massacre raises serious questions about the types of background checks conducted for government contractors and pledged to open an investigation.

"We going to drill down on it," Carper said, speaking to reporters in the Capitol. "What can we learn from this awful experience to reduce the likelihood of future attacks?"

Carper, a Delaware Democrat, said he doesn't know whether across-the-board budget cuts known as the sequester played a role in the security at the Navy Yard on Monday. But he and other senators demanded answers for how Aaron Alexis, the suspected killer with a police record, could have received clearance to work as a federal government contractor.

Sen. Kelly Ayotte, R-N.H., called for Senate hearings to study the hiring practices of federal contractors at military installations.

"In the wake of this tragedy, we must thoroughly review and fix deficiencies within existing federal contracting hiring practices that the alleged Washington Navy Yard gunman exposed and exploited, to ensure the safety of the rest of our service family - service members, civilian workers, and contractors, alike," Ayotte said. "It is with this in mind that I request a committee hearing as soon as possible to examine these important issues."

Sen. Lindsey Graham, R-S.C., echoed the concern and said the suspected Navy Yard shooter, along with Edward Snowden, who leaked national security secrets, were troubling back-to-back examples of how new steps need to be taken for government contractors.

"What are we doing to check who works for the government in a civilian capacity?" Graham said. "Is it because we don't have the resources or is the system just fundamentally broken? I don't know, but of all the things I've heard about the Navy Yard, the question that looms the largest to me: How could he even get the job to begin with?"