WASHINGTON — The wounding of Rep. Gabrielle Giffords in a Tucson, Ariz., shooting spree that killed at least five people, including one of her aides and a federal judge, follows a dramatic increase in threats against members of Congress over the past year.

In the first three months of 2010 alone, officials reported 42 threats to federal lawmakers, nearly three times the cases reported during the same three months a year earlier. In March, someone either kicked in or shot out a window in Giffords’ Tucson office just hours after the Arizona Democrat voted for an expansion in government-directed health care.

A day later, Giffords also was among 20 House Democratic supporters of the health care bill who were the subject of a posting on former Alaska Gov. Sarah Palin’s Facebook page encouraging people to organize against their re-election. The posting featured a map of the United States, with the cross-hairs of a gun scope imposed over each of the 20 Democrats’ districts, all won by the John McCain-Palin GOP presidential ticket in 2008.

In a March 25 interview with MSNBC after Palin’s posting, Giffords said political leaders should be cautious about how they reach out to supporters. She said political leaders need to get together and say "look, we can’t stand for this."

"We’re on Sarah Palin’s targeted list," she said at the time. "But the way she has it depicted she has the cross hairs of a gun site over our district."

She warned: "When people do that, they got to realize there are consequences to that action."

After news of Giffords’ shooting, Palin offered the lawmaker and the other victims her condolences.

"On behalf of Todd and my family, we all pray for the victims and their families, and for peace and justice," Palin wrote on her Facebook page Saturday.

Giffords beat a tea party favorite in November to win her third term in office.

On Saturday, she was shot in the head while holding a forum for constituents in a grocery store parking lot; doctors expected her to survive. People familiar with the investigation identified the gunman as Jared Loughner, 22, of Tucson. The motivation for the shooting was not immediately clear.

In one of several YouTube videos, Loughner complained about literacy rates in Giffords’ congressional district and repeatedly complained about the government.

Unrest over the sweeping health care bill, now law, prompted a rash of threats and vandalism in the spring. Bricks were hurled through Democrats’ windows, a propane line cut at the home of a congressman’s brother and menacing phone messages left for lawmakers who supported the bill.

At the time, the FBI and Capitol Police briefed Democratic lawmakers on how to handle security threats. Normally only those in leadership positions have personal security guards.

After Saturday’s shooting, U.S. Capitol Police sent messages to congressional offices advising lawmakers and their aides "to take reasonable and prudent precautions." Capitol Police, the FBI and the Pima County, Ariz., sheriff’s office were investigating the shooting.

Three of Giffords’ staffers were shot in the attack, said C.J. Karamargin, a spokesman for the congresswoman. One died, and the other two are expected to survive. Gabe Zimmerman, a former social worker who served as Giffords’ director of community outreach, died.

Also killed in the shooting was John Roll, the chief judge for the federal court in Tucson. Roll had received telephone threats after ruling in 2009 that a $32 million civil-rights lawsuit filed by a group of illegal immigrants against an Arizona rancher could go forward.

In Washington, Speaker John Boehner, the Ohio Republican who took control of the House on Wednesday, said: "An attack on one who serves is an attack on all who serve. Acts and threats of violence against public officials have no place in our society. This is a sad day for our country."