WORCESTER, Mass. – Students and staff in Worcester Public Schools are mourning the death of a beloved instructional assistant after police believe she was strangled in her apartment by an illegal immigrant with a lengthy criminal record.

“All her life she was a very kind person,” Superintendent Maureen F. Binienda said of Sandra “Buffy” Hehir, who was found dead in her apartment by a neighbor on Feb. 5. “I really hope that people join together to find who did this.”

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On Monday, Worcester police arrested 54-year-old Jose Melendez based on DNA evidence recovered from the crime scene. Immigration and Customs Enforcement officials confirmed to Breitbart that they’ve placed a detainer on the career criminal, who also goes by Alvarado and Segura.

Melendez, who was also wanted in connection to two drug cases in Warcester, was arrested last week on a warrant for a probation violation from a different breaking and entering case in 2014, the Boston Globe reports.

He was arraigned on Monday in Worcester District, where Judge Margaret Guzman ordered him held without bail. Melendez, who denied knowing Hehir or being in her apartment, pleaded not guilty and is expected back in court for a hearing on April 13, MassLive.com reports.

“If released to ICE under any circumstance, Melendez will face deportation,” according to Breitbart.

DNA from a previous unsolved rape case from 2000 led police directly to Melendez.

“DNA was collected from the crime scene. When it was uploaded to the Combined DNA Index System, it matched DNA from an unsolved Worcester rape in 2000, according to prosecutor Cheryl Riddle,” MassLive reports.

“Melendez was a suspect in the 2000 rape case. He consented to have a DNA swab test in this case.”

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“His DNA was compared to the evidence from the crime scene and is a match,” Riddle said.

Melendez has also faced charges in New York and Florida, MassLive reports.

Superintendent Binienda and others who knew and worked with Hehir, 49, had nothing but good things to say about the former middle school instructional assistant who graduated from the local South High Community School in 1985, according to the Telegram.

“She was just a wonderful person,” said John Bradley, Hehir’s former brother-in-law and close friend. “Very friendly, sociable, very healthy – very into running and taking care of herself.”

Binienda said she taught Hehir at South High and she was a “great athlete, very smart – had lots of friends.

“Lots of friends – everybody knew Buffy,” she said.

“If you ever needed a good laugh, she was the one that would give it to you,” close friend Carrie Gladden told the news site. “She really would give you the shirt off her back.”

Gladden said Hehir’s father died shortly after she was born, and she quit her job years back to take care of her mother with cancer before resuming teaching when Carol Hehir died in 2010.

“She loved kids,” Gladden said. “She wanted to make an impact on all the kids she taught, and she did.”

Hehir taught in Worcester Public Schools for over a decade, most recently at Claremont Academy.

“Buffy greeted all students daily with a smile and shared her message of the importance of earning a high school diploma, continuing on to college or vocational training, making good decisions and treating others with kindness,” her obituary read.

The courtroom was packed with Hehir’s friends and family at Melendez’ arraignment Monday, and they released a prepared statement about the tragedy after the hearing.

“The family would like to thank the Worcester Police Department Detective Bureau for their hard work, especially Sgt. Mark Richardson,” the statement read. “We would also like to thank the Worcester School Department, especially Maureen Binienda, for the kindness and compassion shown to us during this difficult tragedy. We are grateful that a suspect has been arrested and we are looking forward to justice for Buffy.”