A man allegedly involved in the killing of a witness in a BSP MLA's murder case last month was shot dead in an encounter, Uttar Pradesh police said today. According to police, Usman was one of the six shooters who pumped bullets into Umesh Pal, a key witness in the 2005 murder of Bahujan Samaj Party legislator Raju Pal, on February 24. Two policemen on Umesh Pal's security duty, died of injuries later.