Confusion reigned on Capitol Hill Monday after the Senate went into lockdown mode in the wake of a deadly shooting about a half-mile away at the Washington Navy Yard.

Police didn’t keep people from entering or exiting the Senate building until 3:06 p.m., however — nearly seven hours after reports of the shootings that left 13 people dead.

Roughly an hour and 15 minutes later, the lockdown was partially lifted.

In another discordant note, the House, which is actually closer to the Navy Yard than the Senate, never took the step of locking down.

Word of the shooting spread Monday morning; it was later confirmed that a suspect, 34-year-old Aaron Alexis, was killed in an exchange of gunfire with police.

Police said initially that they had no concern about the safety of people in the Capitol, even though the shooting took place just blocks away and there had been reports of multiple suspects.

That assessment seemed to shift by the middle of the afternoon. In an email to Senate offices at 3:06 p.m., Senate Sergeant-At-Arms Terrance Gainer wrote that he had consulted with the U.S. Capitol Police and decided to lock down the Senate complex.

“In light of the uncertainty surrounding the shooting at the Navy Yard this morning and particularly the possibility of suspects remaining at large, we have decided to lock down the Senate complex,” Gainer wrote. “You may move about the building; however, for the next two hours you may not leave nor can anyone enter the building.

“This will be in effect until we deem the situation safe in the neighboring community.”

Gainer’s announcement came about an hour after Senate Majority Leader Harry ReidHarry Mason ReidDems search for winning playbook Dems face hard choice for State of the Union response The Memo: Immigration battle tests activists’ muscle MORE (D-Nev.) said he would cancel the rest of the Senate’s planned workday in light of the shooting. Senators had planned late-afternoon votes on two judicial nominees, which are now likely to take place Tuesday.

The Senate’s announcement led to some confusion in the Capitol, as there was no announcement from the House side as to whether the House would be shut down. The House and Senate chambers are in different wings of the Capitol, and both chambers — as well as all House and Senate offices — can be accessed by underground tunnels and passageways.

Congressional aides speculated that there was no House lockdown because the House was not in session on Monday, although there were staffers in both House and Senate offices.

Adding to the confusion were reports that senators were allowed to enter and exit the building, while all others had to stay in place.

At 4:16 p.m., Gainer sent another email to Senate offices saying the lockdown had been partially lifted in order to allow people to leave for home.

“Although we do not have any more information on the second alleged shooter, given the time of day and your personal family obligations, I am lifting the portion of the lock down which required you to remain in the buildings,” he wrote. “No one other than staff will be allowed to enter the Senate facilities until regular business hours tomorrow.”

Gainer also offered a more detailed justification for the lockdown, including reports of multiple shooters. He also cited past shootings as a reason for his abundance of caution.

“While this approach is inconvenient, it is at times necessary,” he wrote. “The lessons of Boston, Virginia Tech, Sandy Hook, and Aurora are clear, and just still too raw.”

—This story was posted at 3:26 p.m and updated at 8:36 p.m.