She told more than 100,000 followers: “The world is very obviously changing right now and if you ever needed to pick a side, the time to do right in your life is now.”

Partner ‘stabbed through the heart’

In the early hours of Monday morning, Johnson fatally stabbed her partner, Jaelen Allen Chaney, at their apartment in the San Fernando Valley area, about 25 miles (40km) north west of downtown Los Angeles.

The couple had an argument that turned violent, and detectives found a knife “with biological evidence” at the scene, authorities said.

Police who went to the family apartment found a trail of bloody footprints and the body of Chaney, a 29-year-old US Air Force veteran. He had been stabbed in the heart.

“Their door was wide open, there was blood on the floor leading into their apartment, and then a trail of it in the hallway leading up to the elevator and I saw some blood on the walls,” one of Johnson’s neighbours told LA’s KABC-TV.

According to the Los Angeles Times, Johnson tried to drag her partner’s bloody body out of the apartment, but gave up and dragged the body back into the apartment kitchen.

After killing Chaney, Johnson then fled in a dark-coloured Porsche Cayenne SUV.