Scientists accidentally killed the once known world's oldest living creature, a mollusc, known to be aged as 507 years old.

The given statement is true. Scientists did accidentally kill the world's oldest living creature, a mollusc known to be aged as 507 years old. This incident occurred when researchers were trying to determine the mollusc's age by opening its shell, resulting in the creature's death. However, it is important to note that these accidental deaths sometimes occur in the pursuit of scientific knowledge, as researchers aim to gather information to better understand and protect these long-lived organisms.