PLAINFIELD, Ill. (WLS) -- Four people were injured after being attacked by their family dog Saturday in southwest suburban Plainfield, police said.The attack occurred shortly after 9 p.m. in the 22900-block of Judith Drive.Upon arrival, officers were able to gain partial control of the dog, which was a pit bull, but it was "euthanized" due to its aggressiveness.A 25-year-old man suffered severe injuries to his arms and was taken to St. Joseph Hospital in Joliet, police said. He was then transferred to Loyola Hospital in Maywood.Three other people, a 52-year-old woman, 25-year-old woman, and 19-year-old man, were also treated for injuries and released from the hospital, police said.Police said their initial investigation shows the attack was unprovoked.The Plainfield Police Department and Will County Animal Control are investigating.