Conversation so far:
do Tour De France riders have to wear helmets
In 2003, the UCI added helmet wear to their list of rules. In 2014, they changed the rules again, allowing cyclists to forgo their helmets during the first two stages
What caused the enforcement of the rule of compulsory helmet wear in the UCI on 2003
In 2003 the UCI made helmets compulsory after race participant Andrei Kivilev had an unfortunate collision with another rider and his head injuries caused his death a short time after.

Question: Who said that was the reason for the death
Self-contained rewrite: Who said that the death of Andrei Kivilev was from head injuries