On Tuesday (Sept. 8) Lupita Nyong’o paid tribute to her late friend and Black Panther co-star Chadwick Boseman with a heart-wrenching Instagram post. The Academy Award-winning actress is the latest to remember Boseman, who tragically passed away late last month.

“I write these words from a place of hopelessness, to honor a man who had great hope,” Nyong’o’s moving post began. “I am struggling to think and speak about my friend, Chadwick Boseman, in the past tense. It doesn’t make sense.”

Nyong’o continued to write that the news of Boseman’s shocking passing is a “punch to my gut” every morning, especially since her former co-star was a person who seemed to possess “an immortal energy.”

“Chadwick was a man who made the most of his time, and somehow also managed to take his time. I didn’t know him for long, but he had a profound effect on me in the time that I did,” she wrote. “When we came together to make Black Panther, I remember being struck by his quiet, powerful presence. He had no airs about him, but there was a higher frequency that he seemed to operate from.”

“…And he put in the work with all of us,” Nyong’o continued. “He showed up to every rehearsal and training and shoot day with his game face on… He set the bar high by working with a generosity of spirit, creating an ego-free environment by sheer example, and he always had a warm gaze and a strong embrace to share.”

“Chadwick’s hands were strong enough to carry the weight of the film and free enough to clasp mine when I needed it,” she added.

Boseman’s death came as a sudden shock to many of his fans and coworkers who were unaware that he had been privately battling colon cancer for the past four years. In her post, Nyong’o wrote that she “never heard him complain” and that he “used his body in every way he could” and even did his own stunts. She noted that he he was “fully alive” and was “fueled by love, not fear.”

“He cared so deeply about humanity, about Black people, about his people,” she wrote. “By pushing through and working with such high purpose in the films he chose to commit to, Chadwick has made infinite his home.”

Nyong’o offered her condolences to Boseman’s family and his wife, Taylor Simone Ledward, and said that she has been unable to accept his passing.

“I’m going to take my time… and in his honor, I promise not to waste my time,” she wrote.

Earlier this month, Boseman’s family held a private memorial service in his honor in Malibu, CA. Nyong’o, Michael B. Jordan and Winston Duke reportedly attended.

Read Nyong’o’s full tribute below.