Death stabbed Sarah appended: He is going to kill people

The American student who was stabbed to death in Rotterdam on Wednesday warned a friend about the impending doom of her roommate: 'He is going to kill people.

ABC News writes this on the basis of WhatsApp conversations. Housemate Joël S. was arrested at a train station and stuck on suspicion of involvement in her death. He is a talented double bass player and won international prizes.