Gerard Hallock has joined FirstService Williams as executive managing director of the firm's Stamford, Conn. office. Hallock will oversee all brokerage and advisory assignments for the Fairfield and Westchester County region of Connecticut. Prior to joining FirstService Williams, Hallock served as a senior managing director at Jones Lang LaSalle.

Jeff Congdon has joined GVA Kidder Mathews as an executive vice president in the firm's San Francisco office where he will focus on institutional real estate investments. Prior to joining GVA Kidder Mathews, Congdon was executive vice president of Helmsley Spear West and Swig Equities.

Kenneth Blomsterberg has been promoted to first vice president of investments for Marcus & Millichap Real Estate Investment Services' Sacramento office. Blomsterberg began his career with the firm in January 1989 and became an associate in August 1994.

Tom Silva has been promoted to senior vice president of The Alter Group, based in Chicago. He will be responsible for all strategic planning and marketing for the group and its affiliates. Previously, Silva was communications director for PM Realty Group, based in Houston.