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 police have released the dramatic 911 calls from Monday's mass shooting inside a bank.

One woman who called 911 said about eight or nine people have been shot. She said she was hiding in a closet in the first-floor conference room.

She told the dispatcher she knew the shooter, who worked with her.

Loud gunshots are heard booming in the background as the employee recounted what was happening.

The dispatcher told the woman to stay quiet and stay where she was. Whispering, she told the dispatcher there was a lot of blood.

The mother of the suspected gunman, 25-year-old Connor Sturgeon, called 911 to say her son's roommate called her and was concerned.

"He apparently left a note," she said.

"He's never hurt anyone, he's a really good kid," Sturgeon's mother told the dispatcher. "I don't know where he would've gotten a gun."

"I know he doesn't own any guns!" she told the dispatcher.

Sturgeon, who was killed by police at the scene, bought the AR-15 used in the attack legally on April 4 in Louisville, according to police.