A former bank employee, armed with a rifle, opened fire at Old National Bank in the U.S. city of Louisville, Kentucky on Monday, killing four people, including a close friend of Kentucky's governor. 

Nine people were also injured, including two police officers. Police say they are investigating the incident and searching for a motive behind the shooting they say Connor James Sturgeon was behind.

Police received reports of gunfire in the bank at 8:38 a.m. (1238 GMT) and were on the scene within three minutes. The suspect shot at officers, who returned fire and killed him.

The attacker livestreamed the tragic incident, which Louisville Metro Police Department Chief Jacquelyn Gwinn-Villaroel called "an evil act of targeted violence." This marks the 15th mass killing and 14th mass shooting in the U.S. this year, emphasizing the alarming increase in gun violence across the country.

This mass murder comes just two weeks after a former student killed six people at a Christian elementary school in Nashville, Tennessee, 160 miles to the south. As the investigation in Louisville continues, authorities are searching for a motive while grappling with the growing rash of mass shootings that raise concerns for public safety and demand effective measures to address gun violence in the nation.

Kentucky Governor Andy Beshear mourned the loss of his close friend Tommy Elliott in the shooting, remembering him as someone who helped build his law career and offered advice on being a good father. The governor's emotional tribute highlighted the personal toll these tragedies take on communities and individuals.

The 15 mass murders in 2023 are the most during the first 100 days of a calendar year since 2009 when 16 had occurred by April 10, according to a mass killings database maintained by The Associated Press and USA Today in partnership with Northeastern University. The years with the most mass killings were 2019 and 2022, with 45 and 42 mass killings recorded during the entire calendar year.

As the nation grapples with these devastating acts of violence, the need for effective solutions to prevent further loss of life becomes increasingly urgent. The recent string of mass shootings highlights the importance of addressing gun laws, mental health, and public safety measures to protect communities and individuals from the growing threat of gun violence.