"My client was a decorated United States Marine. He served his country in combat theater, came back to Chicago and he is serving his city very honorably, and you know what, he doesn't take this lightly," Grace said during an interview with Fox News on Friday night.
"The officer has no cover, he has no concealment, he sees this gun and he sees this individual turning toward him," he said.
Grace said at this point the officer needed to make a split second decision.
"And this is the hardest part, these officers need to make split second decisions of life and death. And he made a decision that was consistent with Chicago police general orders use of force guidelines and with the law," said Grace.
Stillman has been with Chicago police since 2015.
A website that tracks police discipline says there have been three complaints filed against him, for improper searches. One of the complaints was determined to be unfounded. One case was closed, and the third is still open.