Former presidents Barack Obama and Bill Clinton issued pointed calls Sunday for America to stand up and defend their values after the second killing of a citizen in Minneapolis by immigration agents that Donald Trump blamed on Democratic "chaos."

The Trump administration has faced intensifying pressure over its mass immigration crackdown, particularly after federal agents shot and killed Alex Pretti, a 37-year-old ICU nurse, Saturday while scuffling with him on an icy roadway.

That incident came less than three weeks after an immigration officer fired on Renee Good, also 37, killing her in her car in the same Midwestern city.

Trump administration officials quickly claimed Pretti had intended to harm the federal agents -- as they did after Good's death -- pointing to a pistol they said was discovered on him.

However, video shared widely on social media and verified by US media showed Pretti never drawing a weapon, with agents firing at him seconds after he was sprayed in the face with chemical irritant and thrown to the ground.