Brian Wilson "went silent" and "became detached" as he battled the long-term effects of COVID-19, according to his bandmate Al Jardine

Al told Variety: "There was no trauma to speak of until that very last tour in '22. He kind of went silent and began to suffer the effects of long-term COVID, I was told, so I think that was a turning point for him. He became detached."

Brian also suffered mobility issues after undergoing several operations on his back and Al thinks being unable to move around properly affected his pal's mental health.

He explained: "His infirmity must have been really depressing, not being able to walk again."

However, Al is convinced Brian enjoyed his final tour despite his struggles before finally stepping out of the spotlight. He added: "He was with his adoptive family, and we all loved him, and he knew it, and he savoured every moment.

"Until he got on stage. And then he might decide: 'Well, I'm just gonna let them do it.' Who knows what was going through his mind, but he would check out on that last tour.

"And that was hard work for him; he was fragile and tired and exhausted from probably that long-term COVID thing ... So, he became, on stage, not the entertainer that everyone thought they were coming to see."

Brian's family confirmed the late star's passing earlier this week by posting a message on his official Instagram page.

It read: "Our beloved father Brian Wilson has passed away. "We are at a loss for words right now. "Please respect our privacy at this time as our family is grieving. We realize that we are sharing our grief with the world. Love and Mercy."

The Beach Boys added in a statement: "The world mourns a genius today, and we grieve for the loss of our cousin, our friend, and our partner in a great musical adventure.

"Brian Wilson wasn't just the heart of The Beach Boys-he was the soul of our sound.

"The melodies he dreamed up and the emotions he poured into every note changed the course of music forever. His unparalleled talent and unique spirit created the soundtrack of so many lives around the globe, including our own.

"Together, we gave the world the American dream of optimism, joy, and a sense of freedom-music that made people feel good, made them believe in summer and endless possibilities.

"We are heartbroken by his passing. We will continue to cherish the timeless music we made together and the joy he brought to millions over the decades. "And while we will miss him deeply, his legacy will live on through his songs and in our memories. Our hearts go out to Brian's family and his loved ones during this difficult time."