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.
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 the replication pattern 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." (DS9: "Field of Fire")
His personnel file:
Science Officer / Vulcan, Born 2278: S'Lara region
Commissioned to Starfleet as an ensign in 2355, his first assignment was under Capt. Jason Stone aboard the geoterraforming vessel, USS Strata. His record since then has been exemplary, with the exception of a minor note by Strata's Chief Medical Officer, Dr. Martin Rackham, indicating some possible psychological instability.
Prior to his current assignment aboard Deep Space 9, Chu'Lak served aboard the Federation Starship Grissom since 2365. The vessel was destroyed in a battle with the Jem'Hadar at Ricktor Prime. Chu'Lak and five other crewmen were the only survivors.
Chu'lak was played by Marty Rackham.
Robert Hewitt Wolfe commented: "What would be the biggest surprise to a regular Star Trek fan? No one's going to be surprised if a Bajoran or a Cardassian or a Romulan is the killer. But a Vulcan serial killer? That'll make you sit up and take notice. I wanted to show the psychological strains of the War are far-reaching. If you've got a Vulcan who's cracking under the battle, that says something." (Star Trek: Deep Space Nine Companion (p. 651))
In the Star Trek: New Frontier novel, Performance Appraisal, Chu'lak was posted to the USS Grissom as a science officer in 2365. In 2366, he held the rank of lieutenant. In the Deep Space Nine relaunch series story "Ferenginar: Satisfaction is Not Guaranteed" in Worlds of Star Trek: Deep Space Nine, Volume Three, Quark tests Ro Laren's knowledge of Deep Space 9's past, asking her who Chu'lak was. Ro knew he was a Starfleet officer who went on a killing spree, but thought he was Andorian, rather than Vulcan.