Lenny Ross last appears on "Blue Bloods" in Season 13, Episode 20, "Irish Exits." In the episode, Frank Reagan learns that Lenny is suffering from mesothelioma related to the 9/11 attacks on the World Trade Center.
Lenny's last wish is to ride in an NYPD patrol car with sirens blaring. "I want to go somewhere loud and fast," he tells Frank. The two veteran actors were also close friends in real life, and Selleck sent a heartfelt and moving tribute to Williams to PEOPLE after his death.
Selleck wrote, "It has been said that we are all just passing time and occupy our chair very briefly. My friend Treat was aptly named and occupied his chair so well. I will miss him but I will not forget him. Well done, my friend." Bridget Moynahan, who plays Frank's daughter Erin on "Blue Bloods," also shared some kind thoughts about Williams with People. "He was a role model off screen as well," Moynahan wrote. "His love and devotion to his family was one for all to admire. We lost a good one, folks. RIP Treat."
