Donald Trump rushed off stage as possible shots heard at ...

BUTLER, Pennsylvania -- Former President Donald Trump was swarmed by Secret Service agents and rushed off stage as possible shots were heard during a rally in Butler, Pennsylvania, on Saturday.

There appeared to be blood on his right ear as he was being taken off stage, as Trump was seen mouthing "fight" and pumping his fist.

LIVE UPDATES | Trump rushed off stage at rally after possible assassination attempt

A spokesperson for Trump said in a statement, "President Trump thanks law enforcement and first responders for their quick action during this heinous act. He is fine and is being checked out at a local medical facility."

A shooter is dead, Butler County District Attorney Richard A. Goldinger told ABC News.

One bystander is "confirmed dead," and "possibly a second" bystander is dead as well, Goldinger added.

President Biden condemned the shooting at the Trump rally and called on other Americans to do the same.

"The idea that there's political violence or violence in America like this, is just unheard of. It's just not appropriate," he said at a news conference.

Biden said he was trying to get ahold of Trump, who he called Donald, on the phone and wanted to talk to him.

"There is no place in America for this violence. It's sick," he said.

The incident is being investigated as a possible assassination attempt, officials briefed on the situation told ABC News.

The officials said live rounds were apparently fired from outside the security perimeter.

Donald Trump Jr., told ABC News he has spoken to his father, who remains at the hospital. He said his father is "in good spirits" as he remains under observation, adding that his father is "never gonna stop."

Dave McCormick, who's running for U.S. Senate, told ABC News he was in the front row of the rally. He said he heard "seven or eight" shots fired.

"People started to panic," he said. "Everyone dropped to the ground."

Trump began his speech at about 6 p.m. and was only shortly into his speech when a disturbance caused Secret Service to swarm the former president. He was then led off the stage quickly, pumping his fist on stage and also as he was helped into a vehicle to be taken away.

Heavily armed security personnel got on stage as he was led off.

"An incident occurred the evening of July 13 at a Trump rally in Pennsylvania," the Secret Service said in a statement. "The Secret Service has implemented protective measures and the former President is safe. This is now an active Secret Service investigation and further information will be released when available."

The White House said in a statement, "The President has received an initial briefing on the incident at Former President Trump's rally."

"Violence targeted at any political party or political leader is absolutely unacceptable," Pennsylvania Democratic Gov. Josh Shapiro said in a statement. "It has no place in Pennsylvania or the United States."

Ohio Sen. J.D. Vance, a possible vice president pick, wrote on social media, "Everyone join me in praying for our President Trump and everyone at that rally. I hope everyone is ok."

North Dakota Gov. Doug Burgum, a possible vice presidential pick, posted to X, calling for prayers for the former president.

"Please join Kathryn and me in praying for President Trump, his family and everyone attending the rally today."

Another vice presidential hopeful, Florida Sen. Marco Rubio, also posted on X asking for prayers for Trump and those at the rally.

"Praying for President Trump and all those attending the rally in Pennsylvania today."

"ATF is responding to assist the U.S. Secret Service and other law enforcement partners. This is a top priority. We have no further comment at this time," ATF said in a statement.

This is a breaking news report. This will be updated as more information becomes available.