Police say the man, believed to be in his 80s, died at the scene after being attacked in Ealing.
The Tory leadership hopeful said Britons lacked the "application" of foreign citizens, leaked audio suggests.
Ministers were told the Rwandan regime tortures opponents weeks before the first flight was due to go.
The singer, 41, starred on 2002 talent show Pop Idol before having a string of hits and stage roles.
Liz Truss and Rishi Sunak took part in a hustings in Perth to pitch for the votes of Scottish Tory members.