William Shatner took to Twitter on Saturday to express his regret over having to miss Leonard Nimoy’s funeral.

Though the two “Star Trek” actors were very close friends, Shatner explained in a series of tweets that he won’t be able to attend Nimoy’s funeral on Sunday, due to a previous commitment to appear at the Red Cross Ball in Florida Saturday night. Though he will not be present at the funeral, Shatner said he plans to honor Nimoy’s life from afar.

I am currently in FL as I agreed to appear at the Red Cross Ball tonight. Leonard’s funeral is tomorrow. I can’t make it back in time.

— William Shatner (@WilliamShatner) February 28, 2015

I feel really awful. Here I am doing charity work and one of my dearest friends is being buried.

— William Shatner (@WilliamShatner) February 28, 2015

So maybe tomorrow we come together here and celebrate his life.

— William Shatner (@WilliamShatner) February 28, 2015

So let’s spend some time tomorrow celebrating Leonard’s life and remembering the man.

— William Shatner (@WilliamShatner) February 28, 2015

Shatner and Nimoy starred as Captain Kirk and Mr. Spock, respectively, on the “Star Trek” television series and in multiple feature films. Nimoy died Friday at his home in Los Angeles, at the age of 83. Following the announcement of Nimoy’s death, Shatner released a statement expressing love for his longtime friend.

“I loved him like a brother,” he said. “We will all miss his humor, his talent, and his capacity to love.”