NASHVILLE, Tenn. (WTVF) — An accused serial rapist is on the loose and Metro Police is asking for assistance finding him. 20-year-old Willie Williams, Jr. is believed to have victimized seven women in six separate cases. Several of the women are escorts.

According to officials, three arrest warrants have been put out on Williams, charging him with aggravated rape, aggravated robbery and attempted aggravated robbery in two of the six cases.

On June 16, police say Williams contacted a 22-year-old escort via a personals website. She told police they agreed on a price for sex. When Williams showed up at her motel, he pulled a pistol on her, demanded her money and put the gun to her head, demanding her to perform oral sex on him.

On June 19, police say Williams arranged to meet a 29-year-old woman for a date in the parking lot of an apartment complex on Cane Ridge Road. When she arrived, she said Williams sat in the passenger seat of her car while armed with a large knife and demanded her belongings. When she screamed for help, Williams fled from her car.

According to police, Williams is also suspected of sexually assaulting a 26-year-old woman at a motel on Sidco Drive on February 13, two other women who were staying at a motel on Claridge Drive on May 31 and another woman at a Bell Road motel on June 14.

Another woman said he pulled a gun on her and forced her to perform oral sex on him at an Elm Hill Pike motel, after she agreed to buy marijuana from him.

Attempts to locate Williams have been unsuccessful.

Social workers at the Sexual Assault Center in Nashville say it's very likely that the number of sex workers who are victims of sexual assault is much larger than what is actually reported, because they are afraid to contact police themselves.

"A lot of times, victims of sexual assault in this line of work, won't come forward because they think they won't be believed or supported and they think it's all their fault," said Jordan Owens with the Sexual Assault Center.

Williams has a tattoo that reads, "BLESSED," on the front of his neck. He is 6 feet 1 inch tall and weighs 185 pounds. He is believed to be armed.

Anyone who has information on or sees Williams is asked to immediately call Crime Stoppers at (615) 742-7463. A cash reward is available.