Complex sentence: The protests started as a result of the vehicular homicide of 19 years old Angel Petrov, which was allegedly committed by 55 years old Simeon Yosifov, who is believed to be a close associate of Kiril Rashkov.
Split into simpler sentences: The protests started in response to the vehicular homicide of 19 years old Angel Petrov. This was allegedly committed by 55 years old Simeon Yosifov, who is believed to be a close associate of Kiril Rashkov.