Megan McDonald’s loved ones waited 20 years for Thursday's arrest in the cold case.

“We have been given the gift on the beginning of the end,” said Megan's sister, Karen Whalen, during a press conference at the state police barracks in Middletown.

State police said that new DNA technology and new evidence finally linked her ex-boyfriend and longtime person of interest, 42-year-old Edward Holley, to the 2003 Town of Wallkill death.

MORE: Police: Money, jealousy behind ex-boyfriend's killing of Megan McDonald in 2003

“To the district attorney, who is not here today, all eyes are now on you. We are all watching," said Megan's brother-in-law, James Whalen.

Orange County District Attorney Dave Hoovler was noticeably missing during the press conference after Holley’s arrest.

He issued a statement saying his office was never notified that an arrest was going to be made – something that could present a huge challenge for the prosecution ahead.

Rick Trunfio is a former upstate prosecutor who teaches law at Syracuse University.

News 12 asked him to weigh in on the developments.

“This was really an ambush," said Trunfio. "It’s obvious the prosecutor was concerned about the level of proof they had to proceed.”

The DA hasn’t said that but confirmed that his office now has six days to present 20 years of evidence to a grand jury.

Trunfio says it’s unheard of for police not to consult with the DA before filing murder charges – especially on a cold case.

"I’m not saying they have the wrong guy. What I’m saying is that the prosecutor’s burden of proof is fundamental, beyond a reasonable doubt and the real question here is do you want to have the guy in custody for five days or five decades," said Trunfio.

Trunfio says if there’s not enough evidence to indict Holley then the case could be thrown out.

The DA’s office says they’re working diligently to ensure justice for Megan.

State police didn’t comment on why his office wasn’t notified of the arrest, but say they’re prepared to work with prosecutors to make sure Holley is held responsible for her death.