Ashley Van Hemert tells "20/20" about the fateful 2018 night her roommate's estranged husband barged into their home, killed his wife and left her for dead.

Authorities are searching for the man who broke into a Los Angeles-area house and gunned down a father while his wife and son were home, officials said.

At least one person has been shot outside Chicago O'Hare International Airport early Wednesday morning, police said.

At least 12 people have been injured in a shooting at a pub in Toronto on Friday night, police said.

Police responded to a shooting incident at a USPS Processing and Distribution Center in Washington. An adult male victim succumbed to gunshots while the shooter fled.

Southern University and A&M College is a historically Black university system located in Baton Rouge, Louisiana.

The suspect, Diogenes Archangel Ortiz, entered the hospital with handgun and zip ties Saturday morning and took several staff members hostage, state officials said.

A shooting early Saturday morning near an Air Force Base in Albuquerque, New Mexico, left one airman dead and another wounded, authorities said.

Three people were shot and killed in a parking lot outside a driver's licensing office in Louisville, Kentucky, on Friday, police said.

Andrew Lester, the man who pleaded guilty to felony assault in the second degree for the shooting of Ralph Yarl, died while awaiting sentencing.

The FBI arrested two teenage girls plotting a “mass casualty attack” using pipe bombs and guns targeting Memorial High School in Harris County, Texas, police said.

A Florida man has been arrested and charged for shooting 17 bullets at two men who he thought were Palestinians.

A tip to an anonymous hotline leads to arrest of teenager in central Indiana who police say was plotting to carry out a mass shooting at her high school on Friday.

A former rapper is advocating for violent teens to receive a second chance at life.

One person was killed and five others were injured in a shooting at a facility in New Albany, Ohio, police said.

The firearm found on the suspect in the murder of the UnitedHealthcare CEO is believed to have been an untraceable ghost gun, according to police.

"It is a very painful day for all of Sweden," Prime Minister Ulf Kristersson said in a statement posted on social media.

The suspect is among those killed in the shooting, according to a Swedish police spokesperson.

Two people were shot and killed inside a grocery store in Indiana on Monday, officials told ABC News.

Authorities in Florida are searching for the gunmen who "callously" shot and killed a 7-year-old boy. An $18,000 reward is available for information leading to arrests.

A 17-year-old boy who opened fire in his Nashville high school's cafeteria fired a total of 10 shots from a 9 mm pistol within 17 seconds of entering the room.

A social media account connected to the Nashville high school shooting suspect may have been in contact with the suspected Wisconsin school shooter's account.

A 17-year-old opened fire at a Nashville high school on Wednesday, killing one student and wounding a second student, according to police.

A police officer has been seriously injured after a suspect opened fire at authorities from inside a home, officials said.

The FBI is investigating a Border Patrol agent-involved shooting, according to a statement from the Vermont State Police.

A 40-year-old mother was one of six people shot in a New York City convenience store when she was used as a shield by a suspected target, authorities said.

Ten people were shot after several men opened fire at a group of people waiting outside of a music venue in Queens, New York, the NYPD said.

Four family members, including three Americans, were shot in an attack in Durango, Mexico, that left three of the four dead, officials said.

Two people were killed and another six injured in the shooting at Abundant Life Christian School in Madison, Wisconsin, police said.

Police are investigating the online footprint of the 15-year-old girl who allegedly opened fire at her Madison, Wisconsin, Christian school.

Wisconsin has a number of firearm-related laws in effect that limit access to children and individuals with a history of violence.

Gunfire erupted in Towson, Maryland, on Tuesday evening, leaving 1 person dead and 9 others wounded, according to police.

A 15-year-old girl allegedly opened fire with a handgun at Abundant Life Christian School in Madison, Wisconsin, killing a teacher and a fellow student.

The shooting happened inside a classroom at Abundant Life Christian School during a study hall of students from multiple grades, police said.

The shooter was a 15-year-old student, officials said on Monday. Natalie Rupnow, who went by Samantha, died of an apparent self-inflicted gunshot wound.

A teacher and teenage student were killed and six others hurt in a shooting at Abundant Life Christian School in Madison, Wisconsin, on Monday, police said.

The teenage girl alleged to have shot seven victims, two fatally, in an attack on Monday at a Wisconsin school marks the rare occurrence of a female school shooter.

A man was inside the apartment and was arrested and charged with cruelty to children, police said.