During the takeover, it was his job to capture Worf and take him to the top of the embassy where all of the hostages were to be rounded up. However, Worf realized that Kl'rt had a weapon and was able to knock him unconscious with a disruptor blast just as Kl'rt killed Carl Murphy, another embassy employee.
Worf took Kl'rt to the secret sub-subbasement in order to interrogate him. Kl'rt would not tell him anything even under the threat of torture, so Worf simply left him there with no means of escape. After Worf was able to retake the embassy, he retrieved Kl'rt and Kl'rt was turned over to the Klingon authorities.
Weeks later, Worf met with Councillor Kopek in his office as a representative of the Federation to discuss Kopek's opposition to the Klingon-Federation alliance. Kl'rt was hiding in the closet and once again attempted and failed to assassinate Worf who this time, killed Kl'rt in response. Kopek had arranged for Kl'rt to escape from his imprisonment leading Worf to realize that it was Kopek who was behind Klahb the whole time. (TNG novel: A Time for War, A Time for Peace)