Since he heard the sound of the horn but failed to heed the warning, his blood will be on his own head. If he had heeded the warning, he would have saved his life.
KJV
He heard the sound of the trumpet, and took not warning; his blood shall be upon him. But he that taketh warning shall deliver his soul.
ASV
He heard the sound of the trumpet, and took not warning; his blood shall be upon him; whereas if he had taken warning, he would have delivered his soul.