Because logic demanded it.
~ Chu'lak's explanation to Ezri Dax to why he murdered people.

Chu'lak is a psychopathic Vulcan from Star Trek: Deep Space Nine.

He was portrayed by Marty Rackham.


Chu'lak was commissioned into Starfleet in 2355 as an ensign; his first assignment was under Captain Jason Stone on board the USS Strata. While his service was noted as having been exemplary, the Strata's CMO, Doctor Martin Rackham, noted that Chu'lak exhibited some possible psychological instability.

Chu'lak later served aboard the USS Grissom from 2365 to 2375. He was one of six survivors (out of a crew of 1,250) when the Grissom was destroyed by the Jem'Hadar in the Battle of Ricktor Prime.

Following the destruction of the Grissom, Chu'lak was assigned to starbase Deep Space 9, under the command of Captain Benjamin Sisko. During his assignment aboard DS9, Chu'lak was assigned to quarters on habitat ring level D, room twelve.

The loss of the Grissom and the deaths of his friends caused Chu'lak severe emotional problems. He obtained schematics for a TR-116 rifle and modified it to include a micro-transporter and an exographic targeting sensor, which allowed him to kill from his quarters. He chose his victims if they had pictures of people showing any kind of emotion. He killed Hector Ilario, Greta Vanderweg and Zim Brott before he was stopped by Lieutenant Ezri Dax. He claimed that he had committed his crimes because "logic demanded it."