An ITBP constable, accused of killing his senior and injuring another colleague in Mussoorie's Lal Bahadur Shastri National Academy of Administration, surrendered to police here on Sunday, officials said.Indo-Tibetan Border Police (ITBP) constable Chandra Shekhar allegedly shot dead his officer Surendra Lal and injured another colleague on Friday night. He fled the academy campus, 230 km from here, after the incident.Shekhar was agitated over a disciplinary action taken by Lal against him on some issue.The academy is the training ground for IAS officers and those from other services.