Capitol Police sent an e-mail to all House staff in the wake of the shooting of Rep. Gabrielle Giffords (D-Ariz.) at an Arizona event Saturday, cautioning lawmakers to take personal safety precautions.

Giffords and 18 others were shot outside a Safeway in Tucson, Ariz., as she met with constituents during a "Congress on Your Corner" event. 

"The suspect is in custody," the e-mail said. "No further details on the motive or other victims are available at this time."

"The U.S. Capitol Police are directly involved in this investigation," said Sgt. Kimberly Schneider, a spokeswoman for the U.S. Capitol Police. 

The e-mail to members promised that more details would be provided as they became available.

"In the interim, all Members and staff are advised to take reasonable and prudent precautions regarding their personal security," it said.

Adam Sarvana, a spokesman for Rep. Raúl Grijalva (D-Ariz.), was asked whether they had received specific guidance or canceled events this weekend.

"We have no security guidance yet, but I'm sure those decisions will be made soon," Sarvana said.

—Jordy Yager and Russell Berman contributed