News of two more arrests in the case of slain Kansas University student Shannon Martin left her mother at once relieved and disgusted.

“It just horrifies me to think that three people carried my girl off, screaming, to kill her,” Jeanette Stauffer of Topeka said Tuesday.

Police on Monday arrested two men in Golfito, the Costa Rican town where the 23-year-old Martin was stabbed to death May 13, 2001, as she walked home from a disco.

Luis Alberto Castro and Rafael Zumbado, both of whom officials suspected from the beginning but were unable to gather enough evidence against until now, were taken into custody and charged with homicide, prosecutor Erick Martinez said.

Another suspect, Katia Vanesa Cruz Murillo, 27, was arrested in November on the same charge. All three suspects face from 20 to 35 years in jail, Martinez said.

Stauffer learned of the arrests Tuesday morning from an official who called from the U.S. Embassy in Costa Rica.

In late April, Stauffer traveled to Costa Rica with her attorney, her husband and two reporters to see with her own eyes what headway Costa Rican authorities were making in the investigation of her daughter’s death. She left feeling confident Costa Rican and U.S. authorities were doing all they could to bring Martin’s killers to justice.

For the past month, Stauffer said she has suspected investigators were even closer to making an arrest because they hadn’t been returning her phone calls and were evading her questions.

“So I really thought something was going on and they just couldn’t give me clues for fear they would not be able to arrest them, they’d run,” Stauffer said.

Cruz had told prosecutors that Castro and Zumbado stabbed Martin, but the two men have blamed the killing on Cruz, Martinez said.

The motive is still unclear, but police have ruled out robbery and sexual assault.

Martin was in Golfito finishing up research on tropical ferns when she was killed. She was just days from graduating with honors.

KU officials Tuesday expressed relief that the arrests had been made.

“We are gratified by the arrests made Monday in Golfito and hope they will result in charges and convictions in the tragic murder,” university spokeswoman Lynn Bretz said in a prepared statement. “The university and Shannon’s friends and family have waited a long time for these arrests to occur. We thank the Costa Rican government and law enforcement authorities for their persistent and vigilant pursuit of justice in this senseless killing.”

Martinez said the trial could begin in the next few months. Stauffer said she would be there.

“You better believe I will,” she said. “I think that’s when it’s going to be the hardest, just to look at them and wonder why did they have to take my little girl’s future away from her. … She deserved to grow up and have a family and do special things, and they took it away from her.”

The Associated Press contributed to this story