A discarded drinking cup appears to be the key piece of evidence that led to a break in a two-year serial rapist investigation.

That, followed by a confession, was enough to move forward and make an arrest, investigators said.

San Antonio police have filed at least six separate affidavits for arrest involving 18-year-old Anton Jamail Harris, charging him with four counts of aggravated sexual assault, one count of attempted sexual assault, and one count of aggravated robbery.

Investigators wrote that all six cases have positive DNA matches with a sample collected from Harris.

The affidavits state that on June 1 at Marshall High School, after Harris had been identified as a person of interest, he was identified by school police as he sat at a table in the school cafeteria. The affidavit states that when Harris got up and left the area, he left a drink with a straw on the table, and that material was retrieved for DNA testing.

On Thursday, Bexar County Crime Lab testing revealed the DNA profile from the drinking material matched that of the suspect in a continuing series of attacks on women in the Medical Center area, dating back to March 2015.

The affidavit states:

“The analysis of the evidence collected and submitted showed a mixture profile of which the DNA profile collected from the six cases listed cannot be excluded from the mixture analysis from the straw. The suspect the straw was taken from matches the description of the serial rapist in the Medical Center.”

Investigators went on to reveal that they brought Harris in for an interview about the allegations. They said that after he was advised of his rights, Harris confessed to having sexually assaulted a female on May 28, 2017 at the Mission Ranch apartments and a couple of other women going back to 2015.

Investigators said that Harris could not recall the identity of the other victims but stated that some of the sexual assaults happened in the 8000 block of Oakdell Way. The suspect admitted to investigators that he used a handgun during some of the attacks and that he may have cut one of the victims with a kitchen knife in an attack in May of this year.

In each of the cases, the victims described their attacker as being a slender black male in his 20s, wearing a hoodie, a bandana, and brandishing a knife or handgun.

Here is a summary of the affidavits:

March 19, 2015 at the 5600 block of Babcock: A 28-year-old female was aggressively groped as she approached her apartment.

August 15, 2015 at the 8000 block of Oakdell Way: A woman said that she was walking to her apartment when a male placed a black t-shirt over her mouth and nose and put her in a headlock. The victim fought to escape, clawing and scratching the suspect's eyes and face, which prompted the male to let go. The male made a second attempt, but the victim fought back again and the male ran off. DNA was retrieved from under this victim's nails.

June 3, 2016 at the 8000 block of Oakdell Way: A female victim said that, a few minutes after she let her cat out, she heard scratching at the front door of her apartment. She saw nothing through the peephole and opened the door, at which time the male suspect forced his way into the apartment. The suspect was holding a long, metallic knife with a wooden handle. The suspect was shouting "Shut up. Don't scream or I am going to kill you." The victim tried to hide in the bathroom but the suspect caught up to her and held the knife to her throat while sexually assaulting her.

December 22, 2016 at an unknown location: A female victim said that after a third knock at her door, she opened the door and a male suspect forced his way in, threatened her with a knife, demanded money, and sexually assaulted and threatened to kill her.

January 15, 2017 at the 5700 block of North Knoll: A female victim stated that she returned home from shopping and, as she approached her front door, the male suspect pointed a black handgun at her torso. The male forced the victim inside the apartment, pointing the gun at the back of her head. The male demanded money from the victim's wallet and then forced her into a bedroom, where he sexually assaulted her, telling her that if she called police, he would kill her.

May 19, 2017 at the 7800 block of Huebner: A woman reported an attempted robbery. The victim says that she was in her car in the parking lot and she noticed an unknown black male pulling on her vehicle door.

As she exited the vehicle, the male was crouching around her passenger door. The victim said that the male put a knife to her waist and demanded her vehicle. The victim said that the male stated he would stab her if she screamed. She said that she grabbed the edge of the knife and cut her thumb when she pulled away. The victim said that the male fled when another vehicle approached. The description of the male matched the other attacks.

May 28, 2017 at the 5600 block of Babcock: A woman was walking into her apartment and a male forced his way in by putting a gun in the woman's face. The woman said that she was sexually assaulted and the man took her iPhone and iPad Mini.

Harris remains jailed with bonds totaling $750,000. SAPD Chief William McManus believes that there may be more victims. He’s encouraging anyone with information about these attacks to call SAPD’s non-emergency number at 210-207-SAPD.