Wilson was shot dead on January 8 this year, while he was on duty at the Kaliyakkavilai Market Road checkpost near the Tamil Nadu-Kerala border.

The six accused, charge sheeted by NIA in the case, are Abdul Shameem, Y. Thowfeek, Khaja Mohideen, Mahboob Pasha, Ejas Pasha and Jaffar Ali.

They have been charged under various sections of the Indian Penal Code (IPC), including murder, of the Unlawful Activities (Prevention) Act, and the Arms Act.

The case was first registered at the Kaliyakkavilai Police Station of Kanyakumari district under sections of the IPC and the Arms Act on January 9.

Wilson was shot and stabbed to death by Abdul Shameen and Thowfeek in order to create terror in the minds of people including police as part of waging violent jihad, the NIA said, adding it re-registered the case on February 1 and took over investigation from the Tamil Nadu Police.

During the NIA investigation, the roles of other accused viz. Mohideen, Mahboob Pasha, Ejas Pasha and Ali in the larger conspiracy were revealed and they were also arraigned as accused in the case.

During the probe, it was revealed that Mohideen was a member of the proscribed terrorist organisation IS/Daesh.

Since May 2019, he had radicalized Abdul Shameem and Thowfeek (A-2), on the perverted jihadi ideology and recruited them into his terrorist gang to carry out violent attacks against the establishment, especially police, in Tamil Nadu, to bring Islamic Rule or Shariah.

In October 2019, Mohideen had also instructed Mahboob Pasha and Ejas Pasha of Bengaluru and Ali of Cuddalore to procure illegal fire arms and prohibited ammunition for carrying out attacks.

After mid-December 2019, on instructions of Mohideen, Abdul Shameem and Thowfeek were sheltered in Karnataka and Maharashtra by Mahboob Pasha and they were subsequently provided illegal fire arms and prohibited ammunition.

According to the NIA, in early January 2020, when Tamil Nadu Police arrested the associates of Mahboob Pasha from Bengaluru and started pursuing Mohideen, Mahboob Pasha, Ali and others, Mohideen instructed Abdul Shameem and Thowfeek to attack Tamil Nadu Police at check posts along inter-state border in Kanyakumari district.

Consequently, the assailants had travelled to Kaliyakkavilai on January 8 and deliberately attacked Wilson that night.

After committing the terror act, they escaped towards Kerala and concealed the knife and illegal fire-arm used in the attack near the Kerala State Road Transport Corporation (KSRTC) bus stands in Thriuvananthapuram and Ernakulam, respectively.

The assailants further proceeded to Kozhikode, disguised themselves and then travelled to Maharashtra before returning to Karnataka's Udupi, from where they were arrested on January 15, the NIA said.