Dashmesh Regiment sent emails claiming responsibility of the fatal attacks to media houses in Jalandhar yesterday. The email in Punjabi was sent from regimentdashmesh@gmail.Com, police said.
Gagneja was shot on August 6 by two assailants and later succumbed to injuries last Thursday.
The letter, with one Rajinder Singh Jinda as signatory, said,"Gangneja was killed because he was involved in anti-Sikh activities."
"He was taking the RSS' Shakhas to village after village and was trying to make Sikhism a part of the Hindu religion."
Gupta was shot dead at Lalheri Chowk in Khana on April 23.
The police commissioner said efforts are being made to track the IP address from where the e-mail originated and authenticate the letter.