The Police Department recently promoted three of its members and hired three full-time officers. Charles P. Gray, who was promoted from sergeant to provisional lieutenant last year, was promoted to lieutenant. Gray is an 11-year veteran with the department and a commanding officer of criminal investigations, said Chief Paul J. Gallagher. Daniel P. Lanen was promoted from officer to sergeant. Lanen has been with the department for 18 years, and resigned from the Board of Selectmen in October in order to seek the promotion. Daniel J. Crevier, a 14-year veteran with the department, also was promoted to sergeant after serving as provisional sergeant for the past nine months. Brian L. Faye, Steven J. Corr, and Michael J. Reardon were appointed as full-time police officers from reserve officers, pending completion of a 22-week training course that starts Monday at the Police Academy in Lowell, Gallagher said. The new hires are filling existing vacant positions, he said.