In a major breakthrough, the Chhattisgarh police have arrested six persons, including self-styled Naxal commander Barsa Lakhma, who were allegedly involved in the gunning down of 76 security personnel in Dantewada in April."We have arrested six people, including Lakhma, on Sunday night from Morpali," said Superintendent of Police Amresh Mishra.The six were allegedly involved in the killing of 75 CRPF personnel and one state police constable on April 6.