Denver police are looking for a man they say sexually assaulted at least four women in the Lower Downtown area of Denver. Investigators say the circumstances of each assault vary, but in general, the suspect initiated contact with women who were alone and were arranging for or were waiting for a ride. He offered the women transportation and then sexually assaulted them. The suspect's vehicle is described as a sedan. He's described as a black male in his 20's or 30's, with a tall, medium build. Police say there may be more victims and they're warning women to never take rides from strangers.