Former President Obama's former secretary of Homeland Security said Sunday after multiple violent incidents last week that American leaders, including President Trump Donald John TrumpBiden says voters should choose who nominates Supreme Court justice Trump, Biden will not shake hands at first debate due to COVID-19 Pelosi: Trump Supreme Court pick 'threatens' Affordable Care Act MORE, need to turn down their heated rhetoric in favor of "more civil discourse."

"We live now in a very, very toxic environment that includes an incivility in our political discourse among our leaders," Jeh Johnson told ABC's "This Week."

"The attack yesterday and the attempted pipe bombings over the course of last week should be a wake-up call for all Americans to demand change, and change has to start at the top," he said. A shooting at a synagogue on Saturday claimed 11 lives.

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"We’re in an environment now where deranged individuals feel that it’s their place to bring about change in our society with an AR-15 or a series of pipe bombs," Johnson said. "And Americans really do listen to their leaders, including our president."

He noted that the president "has the largest microphone ... the largest bullhorn."

"Americans should demand that their leaders insist on change, a more civil discourse, and a more civil environment generally."

Johnson also argued that social media and internet providers should work to tamp down hateful speech on their platforms.

"I think it’s incumbent upon all of us to be vigilant when it comes to this kind of thing and to demand change among our leaders," he commented, saying that companies have "made great strides to take down truly hateful speech, but they've got to keep at this."

Politicians on both sides of the aisle have decried the shooting Saturday as well as the pipe bombs sent through the mail to several high-profile Democrats last week.

Trump condemned both acts, calling for justice against the perpetrators, as well as unity and a more civil national discourse.

Regarding the attack Saturday, he said, "This evil anti-Semitic attack is an attack on all of us, it is an assault on humanity. It will require all of us working together to extract the hateful poison of anti-Semitism from our world."

However, critics have pointed fingers at Trump for his frequent criticism of the Democratic Party and media leaders who were targeted in the pipe bomb attacks.