President Joe Biden tweeted Monday, "Once again, our nation mourns after a senseless act of gun violence."

“Jill and I pray for the lives lost and impacted by today's shooting. Too many Americans are paying for the price of inaction with their lives," he wrote. "When will Republicans in Congress act to protect our communities?”

White House press secretary Karine Jean-Pierre said at Monday's briefing, "Once again, today the president has called on Republicans in Congress to work together with Democrats to take action to ban assault weapons and high-capacity magazines, to require safe storage of firearms, to require background checks for all gun sales, to eliminate gun manufacturers' immunity from liability."

"These are common sense actions we can ask for and should be getting right now," she said.

"We need to act and we need Republicans to show some courage," she said.

Two officers and seven civilians were injured in the Louisville shooting, according to the University of Louisville Hospital.

One of those officers is in critical condition, according to police.

At least three patients have already been discharged, according to the hospital.

Republican leader and Kentucky Sen. Mitch McConnell, who lives in Louisville, tweeted that he's "devastated" by the news of Monday morning's mass shooting.

"We send our prayers to the victims, their families, and the city of Louisville as we await more information," McConnell tweeted.

His fellow Kentucky senator, Rand Paul, tweeted, "Our hearts break for the families of those lost."

President Joe Biden has been briefed on the shooting, a White House official confirmed to ABC News.

-ABC News' Allie Pecorin and Justin Gomez

Officers arrived at the Old National Bank within three minutes of being dispatched and found the suspect still firing, Louisville police said.

Officers exchanged gunfire with the suspect who died at the scene, police said. It's not yet clear if the suspect's wounds were self-inflicted, police said.

Four victims were killed and eight people are injured, police said.

At least two officers were shot during the exchange of gunfire, police said, including one who is undergoing surgery.

It appears the suspect was a previous or current employee, police said.

"This is awful. I have a very close friend that didn't make it today. And I have another close friend who didn't, either, and one who is at the hospital that I hope is gonna make it through," Kentucky Gov. Andy Beshear said at a news conference.

"The safety of Old National Bank employees and everyone we serve in our banking center locations is paramount,” Jim Ryan, the CEO of Old National Bank, said in a statement. “As we await more details, we are deploying employee assistance support and keeping everyone affected by this tragedy in our thoughts and prayers."

Nickolas Wilt, the rookie Louisville police officer shot in the head while responding to Monday's shooting at Old National Bank, is "slowly improving," city authorities told ABC News Wednesday morning.

Wilt remains in critical condition, however. He was the only victim still listed in critical condition.

-ABC News' Will McDuffie