Complex sentence: American heavy metal band Pantera, noting the similarities between Grimmie's murder and the deaths of former Pantera guitarist Darrell Abbot and three others, urged concert promoters and club owners to impose better security measures to protect artists from gun wielding fanatics.
Split into simpler sentences: American heavy metal band Pantera issued a collective statement due to the similarities between Grimmie's murder and the deaths of former Pantera guitarist Darrell Abbot and three others. Pantera urged concert promoters and club owners to impose better security measures to protect artists from gun wielding fanatics.