Barack Obama was sworn in as America's 44th president 1,425 days ago. Since then, five of the 12 deadliest mass shootings in our history have happened. Here they are, as well as other lesser mass gun-killings that happened under his watch.

Sandy Hook Elementary
If the current death toll holds, the 27 gun deaths today at Sandy Hook Elementary School will rank as the second-deadliest mass shooting in U.S. history, according to this Washington Post list.

Binghamton Immigration Center
On April 3, 2009, naturalized immigrant Jiverly Wong shot and killed 13 people and himself at the American Civic Association immigration center in Binghamton, N.Y. He left a note complaining about harassment from the police and his inability to get a job. It was the eighth deadliest mass shooting in U.S. history.

Ft. Hood
On November 5, 2009, Army Maj. Nidal Malik Hassan shot and killed 13 soldiers at Ft. Hood near Killeen, Texas. It was the ninth deadliest mass shooting in U.S. history.

Aurora, Colorado
On July 20, 2012, medical student James Eagan Holmes shot and killed 12 people inside a movie theater showing The Dark Knight Rises. It was the 11th deadliest mass shooting in U.S. history.

Geneva County, Alabama
On March 10, 2009, Michael Kenneth McLendon shot 10 people, two of them children and several of them his own family members, in a spree spanning the towns of Geneva and Samson, Ala. It was the 12th deadliest mass shooting in U.S. history. Those are the ones that rank. What follows is a partial list of other gun massacres that have taken place over the last four years.

Portland Mall Shooting
On December 11, 2012—three days ago—a masked gunman named Jacob Roberts entered a Portland, Ore., shopping mall and shot and killed two people before taking his own life.

Sikh Temple
On August 5, 2012, Wade Michael Page shot and killed six worshippers at the Sikh Temple of Wisconsin in Oak Creek, Wisc., before taking his own like.

Gabrielle Giffords
On January 8, 2011, Jared Loughner shot and killed six people—including 9-year-old Christina Green—at a mall in Tucson, Ariz. His target, who survived a gun wound to the head, was Rep. Gabrielle Giffords.

University of Alabama-Huntsville
On February 12, 2010, University of Alabama-Huntsville biology professor Amy Bishop shot and killed three colleagues during a faculty meeting.

Santa Clara Massacre
On March 29, 2009, software engineer Devan Kalathat shot and killed his two children, his brother- and sister-in-law, and their 11-month-old.

Carthage Nursing Home
On February 12, 2010, Robert Stewart shot and killed eight people at the Pinelake Health and Rehab convalescent home, where his estranged wife was a nurse. His wife survived.

Minneapolis Sign Company
On September 27, 2012, Andrew Engeldinger shot and killed five co-workers at Accent Signage Systems in Minneapolis, Minn., shortly after he was fired.

Seattle Coffee House
On May 29, 2012, Ian Stawicki shot and killed five people and himself in a spree that began at Cafe Racer Espresso in Seattle, Wash.

Tulsa, Okla.
April 6, 2012, white supremacists Jake England and Alvin Watts shot and killed three black pedestrians in Tulsa, Okla., in a racially motivated attack.

Oikos University
On April 2, 2012, a mand named One Goh shot and killed seven people at Oikos University, a Korean Christian college in Oakland, Calif., where he had previously studied.

Seal Beach Salon
On October 12, 2011, Scott Dekraai shot and killed eight people at the Salon Meritage hair salon in Seal Beach, Calif.

Nevada IHOP
On September 6, 2011, Eduardo Sencion shot and killed five people at an IHOP in Carson City, Nev.

Connecticut Beer Distributor
On August 3, 2010, Omar Thornton shot and killed eight co-workers and himself at Hartford Beer Distributor in Manchester, Conn., after he was caught stealing.

[Via Thing Progress; images via AP]