. >> police later identified her as linda gibson. was 39. >> she was a gal that lived in kalamazoo. we had dealings with her in the police department. >> she was tiny. she couldn't have done nothing to anybody. >> donna alsup is linda's sister. she said linda led a difficult life, resorting to prostitution to feed a drug addiction. donna always feared for linda's safety, but wasn't prepared for this. >> it was senseless. to me, what i seen is not going to ever go out of my mind. never. >> her throat had been cut. >> and yet there wasn't much blood. >> there was hardly any blood, yeah, which led us to believe she wasn't killed there. >> there was a surveillance camera in the area. did it pick up anything? >> yes. there was a business that was located at the dead-end of the street. and it picked up a vehicle that appeared to be a brown van. >> but no license plate or driver was visible. with little to go on, cordes hit the street looking for leads. >> where did you look first? >> we started looking at what we call johns, people that wer