Another shooting incident – this time in Colorado -- has brought attention to the debate about gun violence in the United States.
"Enough is enough," said President Barack Obama on Saturday.
A police officer and two civilians were killed Friday during a five-hour shooting spree in Colorado Springs, Colorado. Nine other victims were wounded.
The shooting happened at a Planned Parenthood healthcare facility.
The man accused in the shooting, Robert Lewis Dear, was due in court Monday. Dear's motive for the attack is unknown, but he reportedly talked about abortion during the shooting.
Planned Parenthood is a national provider of health and family planning services. It tests for sexually transmitted diseases and offers health consultations.
Some of its health clinics provide services to end pregnancies. Abortion has been legal in the United States since 1973. But it is very controversial.
Fifty-five percent of American adults say abortions should be legal in all or most cases, compared with 40 percent who say it should be illegal all or most of the time, according to a February 2013 Pew Research poll.
The Justice Department said the case may qualify as a domestic terrorism crime.
Gun violence is a controversial topic in the U.S. The U.S. Constitution allows for the "right to bear arms." But modern understanding of the Second Amendment to the Constitution has been heated.
The day after the Colorado shooting, the University of Chicago received an online threat of violence. The university canceled classes Monday because of the threat of gun violence. The school also increased police and securitypatrols. It ordered students in college housing to stay inside Monday.
The university is five blocks from President Obama's Chicago home.
In December 2012, a heavily armed young man shot and killed 26 people at Sandy Hook Elementary School in Newtown, Connecticut. Six were adults, but 20 were children in Grade 1. The shooter killed himself when police arrived.
Since then, 74 other school shootings have occurred, said politifact.com.
After Sandy Hook, public opinion shifted toward support for gun control, according to a Pew Research Center poll in 2013. Fifty percent of those polled said gun control was the most important issue. Before the Sandy Hook shooting, 40 percent said gun control was the most important issue, according to a Gallup poll.