There have been at least 15 mass shootings in the U.S. in the first 10 days of April, including Monday morning's shooting in Louisville, according to the Gun Violence Archive.

So far this year, the nation has seen at least 146 mass shootings.

The Gun Violence Archive defines a mass shooting as at least four people shot, not including the suspect.

“It feels like every day in this country we are totally consumed by yet another mass shooting. Nowhere else in the developed world do people wake up to this preventable horror every single morning," Kris Brown, president of the Brady Center to Prevent Gun Violence, said in a statement Monday. "Whether it's a bank, a school, a supermarket, or a church, Americans no longer feel safe in their communities. And Americans are increasingly tired of living in fear of being a victim of a mass shooting."

“It does not have to be this way," Brown said. "But until the gun industry no longer has a vice grip on our elected officials, this will continue to be our daily reality."

-ABC News' Ahmad Hemingway

The gunman opened fire in the Old National Bank's first-floor conference room at about 8:30 a.m. local time, according to officials.

Eyewitnesses said the shooter appeared to have been armed with a long gun.

"He just started shooting," Troy Haste told ABC Louisville affiliate WHAS. "Whoever was next to me got shot. Blood is on me from it."

Police said the suspect is dead.

A responding police officer was shot in the head, sources told ABC News. The officer’s condition is unknown.

According to preliminary information, this shooting is not believed to have been terror-related, sources told ABC News.

-ABC News' Jack Date, Josh Margolin, Luke Barr and Aaron Katersky

Louisville police tweeted that the "suspected shooter has been neutralized," adding, "There is no longer an active aggressor threat."

Louisville Mayor Craig Greenberg tweeted that residents should avoid the area around Slugger Field until further notice.

Kentucky Gov. Andy Beshear said he is heading to the scene.

"Please pray for all of the families impacted and for the city of Louisville," he tweeted.

FBI and ATF agents are assisting with the incident.

Louisville Deputy Chief Paul Humphrey provided a timeline of the police response to Monday's shooting while sharing body camera footage from the responding officers:

--8:38 a.m.: Officers dispatched.

--8:41 a.m.: Officers Nickolas Wilt and Cory Galloway pull up to an entrance to the bank. Gunshots are immediately fired in their direction, forcing them to back up the car.

--8:42 a.m.: They exit the vehicle.

--8:44 a.m.: Wilt is struck and officers return fire. When Wilt is struck, Galloway is heard yelling, "He’s down! Get the officer!”

--8:45 a.m.: After a short barrage of gunfire, officers make entry to the bank and confirm the suspect is down.

-ABC News' Will McDuffie