Bill Cosby has paid tribute to his Cosby Show on-screen son Malcolm-Jamal Warner, who drowned while on a family trip in Costa Rica on Sunday. Cosby's spokesperson, Andrew Wyatt, told People that Warner's tragic death "reminded him of the same call he received when his son died." (Cosby's son, Ennis Cosby, was murdered in 1997 during an attempted robbery on a Los Angeles freeway ramp as he tried to change a flat tire. He was 27.)Authorities said Warner's official cause of death was asphyxia, caused when the body is deprived of oxygen.