Sasha Alexander, the actress who played her, wanted out of the show. They wrote her out with the death of her character; here's what happened:
Ari Haswari killed her. There was a raid at a warehouse (episode Twilight) and on the roof Kate jumps in front of a bullet that was headed towards Gibbs and took it in the chest (she had a vest on.) She was knocked down by the force, and after Tony and Gibbs helped her up, she was shot in the head by Ari Haswari.
Kate was shot in the middle of the head by a sniper wich happens to be zivas brother
Washington DC
No. Kate was just played by one person - Sasha Alexander
Todd
We never found out on the show.
She was awarded the Presidential Medal of Freedom posthumously
She was shot and killed by agent David's brother Areies on a roof top after saving agent Gibb's.
No
No. She died.
Washington DC
No. Kate was just played by one person - Sasha Alexander
Todd
Gibbs and Gearld
We never found out on the show.
Wendy Makkena
She was awarded the Presidential Medal of Freedom posthumously
The episode mentioned above is Bete Noir, which was aired in Season One of NCIS.
Kate Todd is played by Sasha Alexander, who left the season for personal reasons. Her character, Kate, is an ex-Secret Service agent who was invited to join NCIS by Agent Gibbs after she disobeyed a superior. She did not leave for personal reasons, she died, shot by Ari, Ziva's half-brother.