Updated: 9:29 p.m.

Following the shooting of Rep. Gabrielle Giffords (D-Ariz.), the top official in charge of House security is urging Members and staff to be aware of their surroundings and report suspicious activity to local law enforcement and the Capitol Police.

“I strongly urge Members and staff to be continuously aware of their surroundings and to immediately report circumstances that appear suspicious,” House Sergeant-at-Arms Bill Livingood wrote in an e-mail to Members and staff. “If you are scheduled to be in a public forum (town hall meetings, rallies, etc.), and feel uncertain about your safety, immediately contact the U.S. Capitol Police Threat Assessment Section or the Sergeant at Arms.”

The section monitors threats and unlawful activity directed toward Members of Congress.

Livingood added that it is important for each district office to establish communication with local law enforcement, who can provide added security if necessary.

Livingood’s e-mail comes about eight hours after Giffords was shot in the head at a Safeway in Tucson, Ariz.

The Capitol Police department said earlier in the day that the suspect in the Arizona Democrat’s shooting is in custody and also urged Members and staff to be cautious.

The Capitol Police department said the suspect in the shooting of Giffords (D-Ariz.) is in custody but has urged Members and staff to be cautious.

“The United States Capitol Police has communicated with House Members of Congress advising them to take reasonable and prudent precautions regarding their personal safety and security,” Capitol Police spokeswoman Sgt. Kimberly Schneider said in a statement. “We are currently working with Federal, state and local law enforcement agencies.”

She added that the police remain at a “high level of readiness, consistent with our operating conditions on U.S. Capitol Grounds, and we continue to maintain a robust presence.”

There was no noticeable increase in police presence at the Capitol grounds Saturday afternoon.

A Democratic chief of staff slammed the department, noting that it took them more than two hours to alert lawmakers. According to an e-mail obtained by Roll Call, the notification was sent out to House staff at 3:16 p.m.

“That is incredibly scary. We have Members all across the country doing events right now,” the chief of staff said. “The response by the Capitol Police is inept.”

The aide noted that Capital Police routinely sends out timely notices about threats in and around the Capitol. “We get announcements about suspicious packages within 15 seconds,” the aide said.

At 4:26 p.m., an alert was sent to all Senate staff informing them, “There is no indication at this time that this event is part of a larger threat against the Congressional membership or has a nexus to terrorism but the investigation is ongoing.”

“The Senate Sergeant at Arms Office is actively involved in monitoring this event, assessing any additional or expanded threats and working with the U.S. Capitol Police,” the alert read. “As more information is confirmed it will be provided. In the interim, if Members are in a public forum or scheduled to be in a public forum and feel uncertain about their safety, they should contact the U.S. Capitol Police immediately.”

Several Members, including Minority Leader Nancy Pelosi, had public events scheduled for Saturday. A spokesman for California Democrat said the San Francisco event would proceed as scheduled.

When reached by phone Saturday afternoon, Senate Sergeant-at-Arms Terrance Gainer, a former police chief who sits on the Capitol Police board, said he is not in a position to comment and that his office is trying to work out its next course of action.

Former Senate Sergeant-at-Arms Bill Pickle said it’s common policy for Members to get an extra protective detail when intelligence indicates they may be in danger.

But with 535 Members, Pickle added, the Capitol Police does not have the resources to protect everyone all the time. Instead, Members rely on local law enforcement to protect them during public events, he said.

“The only people who have full-time protection in Congress are Members of leadership,” Pickle said. “I don’t think there’s anything more the Capitol Police could have done. They don’t have the resources to do more than what is normally done.”

Capitol Police did not say whether Giffords had a protective detail, citing department policy not to comment on Member security.

Pickle said that he’s confident the Capitol Police will send investigators to Arizona to oversee the investigation into Giffords’ shooting and find out whether there should have been more security.

“It’s safe to say the Sergeant-at-Arms of both the House and Senate will ask the police to conduct a complete review of what happened to try to determine that there had been any threats against her and any intelligence that would have perhaps caused them to be more involved,” Pickle said.

“There is no place in our society or discourse for such senseless and unconscionable acts of violence,” said Homeland Security Secretary Janet Napolitano, a former two-term governor of Arizona.

A spokeswoman for Rep. Dan Lungren, chairman of the House Administration Committee, which oversees the Capitol Police, said the California Republican has been briefed.

“Mr. Lungren and his staff have been briefed on today’s tragic incident and are working with House Leadership and House security officials to ensure that the necessary security measures are in place,” Salley Wood said.

Jackie Kucinich and John Stanton contributed to this report.