Come to Washington, and you learn some new terms. The Hill refers to Congress. Langley is the CIA. And if someone asks if you have a clearance, they want to know if you’ve passed a background check — not whether the team doctor says you’re ready to get back on the field.

If you answer “yes,” you’re far from alone. Nearly 5 million Americans hold a security clearance — deceased Navy Yard shooter Aaron Alexis was one of them.

Alexis first gained a security clearance in 2008. He received his clearance despite an arrest in 2004 and a troubling pattern of behavior. He then reportedly passed a reinvestigation earlier this year, despite a 2008 arrest for disorderly conduct, a 2010 arrest for firing a gun in his apartment and a documented history of violent mental-health problems.

Reportedly, the only red flag discovered during his investigation was a traffic violation.

Alexis should not have had access to classified materials or the credentials that allowed him to terrorize a secure military base. That’s clear. But his story prompts other questions: How many others are slipping through the cracks? And why is the security clearance process failing to protect not just Americans’ national security, but now our personal security as well?

As the chairman and ranking member, respectively, of the Senate Homeland Security subcommittee dedicated to overseeing the nation’s federal workforce, we began asking these questions after Edward Snowden’s leak of sensitive information earlier this year.

The answers we’ve uncovered are troubling, and they should prompt deeper investigations and immediate reform to our security clearance and background check investigation process.

In June, we held a hearing that revealed a lack of thorough oversight imperils the security clearance process. Our hearing, conducted jointly with Sens. Claire McCaskill, D-Mo., and Ron Johnson, R-Wis., exposed how the maze of federal employees and contractors conducting investigations lacks accountability, delays timely and complete approval of security clearances, and threatens our national security.

This problem was on full display after last Monday’s attack, when the CEO of Alexis’ contractor said his company never would have hired Alexis if it had known all the details of his personal history. He then said it was the Defense Department’s responsibility to properly vet Alexis’ background.

The Office of Personnel Management, which handles 90 percent of background investigations, contracts much of its work out to private companies — one of which is under investigation for the quality of its work. We now know that this company was responsible for conducting both Snowden’s and Alexis’ background checks.

At our hearing in July, the Office of Personnel Management inspector general told us that because of a lack of authority and resources, he could not perform proper oversight of the 2 million investigations the agency expects to complete this year, leaving contractors and government investigators with no oversight and no accountability.

We immediately introduced a bill, the SCORE Act, to give the inspector general’s office the authority and resources it needs to do its job. Our bill, a critical first step to making sure future Edward Snowdens and Aaron Alexises don’t slip through the cracks, was approved unanimously by the Senate Homeland Security and Governmental Affairs Committee in July. It awaits a vote in the full Senate.

We look forward to working with our colleagues to pass this bill and to help us shine more light on our failing security clearance process.

Getting the agency watchdogs examining the processes is an important first step, but we must ask bigger questions as well. Do 5 million Americans need security clearances? How do we balance the need to thoroughly and efficiently clear qualified applicants with the need to keep our nation safe? And how do we improve the security clearance process at a time when we must get the most out of every taxpayer dollar?

Our subcommittee will look into these questions at our next hearing. In the meantime, we owe it to the Navy Yard victims to take timely and meaningful steps to prevent the next tragedy and do everything we can to reform a process that in many cases is failing to keep Americans safe.

Sens. Jon Tester, D-Mont., and Rob Portman, R-Ohio, are the chairman and ranking member, respectively, of the Homeland Security Subcommittee on the Efficiency and Effectiveness of Federal Programs and the Federal Workforce.