BEXAR COUNTY, Texas -- The Bexar County Sheriff's Office is making headway in the sexual assault case of a San Antonio realtor.

Investigators believe they may have the man responsible for the attack.

Walter Hamilton, 40, is charged with charged with aggravated robbery and is being held at the Bexar County Jail.

Investigators are confident that sexual assault charges will be filed against him.

Hamilton was initially arrested Friday in a dumping ground known for trash and stolen vehicles off of Kyle Seale Parkway.

Sheriff's officials said he was passed out in his car after reportedly over-dosing on pills.

They said they did find items in his car belonging to a woman who was sexually assaulted.

That assault happened last Wednesday at a sales office for a Centex home neighborhood.

Investigators said a man posed as a customer, bound and gagged the victim and left her tied up for several hours.

Officials said that man's description fits that of Hamilton.

"The evidence we recovered from the scene and the evidence we recovered form the suspect and the car he was in, we just have to make the links," said Dale Bennett, of the sheriff's office. "Once we get that done, DNA is one of them."

Investigators said Hamilton has no prior criminal history, but is being held on $100,000 bond.