Christenson was seen on camera extending his right arm in the air as the team was making its way off the field, engaging in an elbow bump celebration with coaches.
Closer Liam Hendriks could be seen correcting Christenson's gesture so it fit what the rest of the team was doing. Christenson then turned around and repeated the gesture.
"No, no straight arm, you have to bend your elbow," Christenson said Hendriks told him, according to the San Francisco Chronicle. "Oh, I see what you mean, oh no, it's like 'Heil Hitler.'"
Teams have moved away from traditional high-fives to follow social distancing rules set forth by Major League Baseball. In a statement Thursday, Christenson said he was attempting to adapt the elbow bump gesture that the team does instead of high-fives and it "unintentionally resulted in a racist and horrible salute that I do not believe in."
"What I did is unacceptable and I deeply apologize," Christenson said in the statement.
The A's said in the statement that they do not support or condone the gesture and "are deeply sorry that this happened on our playing field."