As many as 27 people -- including staff and students -- were killed following a mass shooting at a Newtown, Conn., elementary school on Friday. It marks one of the deadliest school shootings in U.S. history. Here’s a look at other notable tragedies:

Dec. 14, 2012 – A shooting at a Connecticut elementary school leaves as many as 27 people dead, including 18 children. The gunman is found dead inside the school: Sandy Hook Elementary, in Newtown, Conn.

Aug. 27, 2012 – A Baltimore County student was critically injured on the first day of school when he was shot by a gunman believed to be another student. The trial is ongoing.

July 20, 2012 – 24-year-old James Holmes opens fire in a crowded movie theatre in Aurora, Colorado, during the midnight premiere of The Dark Night Rises. Twelve people are killed and 58 wounded. Police arrested Holmes soon after.

April 2, 2012 – A nursing student expelled from a small Korean Christian university in California went on a shooting rampage, killing seven people: six students and a secretary.

Feb. 27, 2012 – A gunman appeared to target a particular student in the cafeteria at Ohio’s Chardon High School just after school began that day. Three people who were shot died in the days after the shooting.

January 8, 2011 – Jared Loughner, 22, shoots Rep. Gabby Giffords in the head during an event near Tucson, Arizona, and also shoots 18 others. Six were shot dead, including a nine-year-old girl and a district court judge.

November 5, 2009 – Forty-three people are shot at the Fort Hood military base in Texas, leaving 13 people dead and another 29 injured. Police charge U.S. Army psychiatrist Nidal Malik Hasan in the massacre. He is currently on trial.

April 3, 2009 – A student taking courses at an immigration services centre in Binghampton, NY, killed 13 people and himself as he walked between the building’s front door and a classroom.

April 16, 2007 – After sending images of himself to NBC that day, an undergraduate student at Virginia Tech university was responsible for the deadliest lone-gunman shooting in U.S. history, killing 32 students and wounding 25. He later committed suicide.

March 21, 2005 – A 16-year-old on Minnesota’s Red Lake reservation killed his grandfather and grandfather’s girlfriend and then nine people at a local school: five students, a teacher and a security guard.

April 20, 1999 – Two students at Colorado’s Columbine High School killed 12 students and a teacherin one of the most notorious school shootings in U.S. history. Both committed suicide afterwards in the school’s library.

Aug. 1, 1966 – A former marine sniper killed 16 people at the University of Texas at Austin, many from the observation deck of a campus tower, before being killed by police.