US school shootings: Deadly attacks as 'model' students become killers

Heres a rundown of the last five deadliest attacks in US schools and universities:

1. Umpqua Community College Shooting

On October 1, 2015, a 26-year-old man identified as Christopher Harper-Mercer committed the deadliest mass shooting in Oregon history, killing nine people and injuring seven others at Umpqua Community College in Roseburg, Oregon.

He only let one person go just so that he could inform the police about the incident. Mercer had suffered from long-term mental illness and was described as "hate filled" by those who knew him.

Some theories behind the mass shooting were Mercer falling below a C average, putting him at risk for suspension, as well as him not being able to pay the tuition bill due.

He ultimately committed suicide after the attack.

2. Sandy Hook Elementary School in Newtown

On December 14, 2012, 20-year-old Adam Lanza shot 20 children and six adults at Sandy Hook Elementary School in Newtown, Connecticut.

Lanza killed his mother, before entering the school where he killed 26 people and injured two others; the majority of his victims were children aging from five to 10 years old.

He committed suicide upon completion of the attack. According to the media and news reports, this was one of the most bizarre shootings because Lanza never offered a motive or reasoning behind the murder of his mother nor the horrendous mass slaying of innocent children.

3. Oikos University Shooting

On April 2, 2012, 43-year-old One L. Goh committed California's deadliest mass killing on at the Korean Christian college Oikos University and killed seven people and wounded at least three more.

He was a former student of the school and opened fire early morning on April 2. Goh had been a nursing student at the college but was not enrolled at the time of the shooting.

Goh apparently targeted a school director he was angry at - but who no longer worked there.

Goh is at Napa State Hospital being treated for paranoid schizophrenia, with his lawyer saying he saw faces in mirrors and experienced delusions regarding "the battle between God and Satan and his role in that battle."

4. Northern Illinois University

On February 14, 2008, Steven Kazmierczak, 27, dressed in black stepped from behind a curtain at the front of a large lecture hall at Northern Illinois University on Thursday and shot 21 people, five of them fatally, then shot and killed himself.

Four died at the scene, including the shooter, and two later died at the hospital. At least 22 people, including a graduate student who was teaching an ocean sciences class, were shot.

The shooter was a graduate student at NIU, he appeared to be a model student, earning a dean’s award in 2006.

He also served as vice president of the Academic Criminal Justice Association, a student group focused on educating the community.

He was treated temporarily for mental illness at the Elk Grove Village Thresholds-Mary Hill House psychiatric center,[33] for being "unruly" at home. Reports said that his behavior seemed to become more erratic in the weeks leading up to the shooting and that it is believed he stopped taking medication beforehand.

5. Virginia Polytechnic Institute and State University

On April 16, 2007, Virginia Polytechnic Institute and State University in Blacksburg, Virginia came under attack when senior student Seung-Hui Cho killed 32 people and injured 17 more in two attacks – one in a co-ed dormitory, the other in the Engineering, Science and Mechanics building.

Cho ultimately committed suicide following the shooting.He is noted as committing the deadliest attack on a school in US history.

Cho was previously diagnosed with severe anxiety disorder; among the tapes he personally mailed to NBC news, Cho expressed his hatred for the wealthy, compared himself to Jesus Christ and explained that he was forced to commit the mass shooting due to voices in his head.