Mission to Krant

Guided by the Force, Darth Kaxs and Darth Toxic found Echuu Shen-Jon and begun fighting him. However, thought Darth Kaxs got him lose his lightsaber, Shen-Jon still managed to kill Darth Toxic. Then Shen-Jon managed to unarm Darth Kaxs by a wellplaced kick.

However, Darth Kaxs had a surprise for the exiled Jedi: the lightsaber of a Jedi Sniper (which he had taken during the Mission to Jedi Temple. However, after taunting and persuading Darth Kaxs, Shen-Jon managed to redeem Darth Kaxs into Kaxs. Kaxs gave Shen-Jon he Sniper lightsaber, and went of to destroy the En'rg-chan Sith Alliance.

Behind the Scenes
This is an explanation to why Echuu Shen-Jon uses a green lightsaber during the Clone Wars and a blue one during the Galactic Civil War; he lost his old one fighting to Sith and got a new one from one of them.