BOSTON -- After saying he would fight extradition to the U.S. to face charges he murdered his wife and baby, Neil Entwistle told a judge in a London courtroom Friday that he would voluntarily return to Massachusetts as soon as possible.

NewsCenter 5's Gail Huff reported that had Entwistle fought extradition, it would have created a lengthy legal battle that could have taken months. He will now likely be arraigned in Framingham District Court, possibly as early as next week.

As he left the Bow Street Magistrates Court, Entwistle mouthed the words to his father, Cliff Entwistle, "Don't worry, Dad. I'm OK."

"He's anxious that a delay may cause his late wife's family, and his own, additional distress -- something he wishes to avoid," his attorney Judith Seddon said.

The British judge asked Entwistle if he was certain he wanted to waive extradition hearings, because his decision would be irrevocable, and Entwistle said yes.

Now, according to an affidavit filed in Hopkinton, Mass., Entwistle told Bay State detectives that he came home from running an errand on Jan. 20 and found his wife and child dead. Prosecutors, however, say that's not possible. They say they have forensics evidence to prove Entwistle was the gunman.

According the affidavit filed in Framingham District Court, "DNA matching Neil Entwistle was found on the grip of the firearm and DNA matching Rachel Entwistle was found on the muzzle end of the firearm."

Three days after the deaths, Entwistle talked to police on the phone, saying he returned to his home about 11 a.m. and found his wife and daughter dead from gunshot wounds.

According to the police affadavit, "He said he did not call for emergency assistance, but instead covered them up and got a knife to kill himself but could not go through with it. He said then he left and drove to his in-laws in Carver to get a gun from his father-in-law so he could kill himself. He said that the could not get into the home so he drove to Logan Airport because he wanted to go home to his parents in England."

Entwistle, 27, was arrested at a London subway stop Thursday as he went to visit a friend. He's facing two charges of murder in the deaths of his wife Rachel, 27, and his 9-month-old baby, Lillian, on Jan. 20.

The Middlesex County District Attorney's office said Entwistle had serious financial problems and he may have contemplated committing a murder-suicide when he allegedly shot his wife and daughter as they lay in bed in their rented Hopkinton, Mass., home. He had reportedly looked for tips on the Internet on how to commit suicide.

"He shot Rachel Entwistle in the head and then proceeded to shoot baby Lillian, who was lying on the bed next to her mother ... we believe that this was intended to be a murder-suicide," Middlesex County District Attorney Martha Coakley said.

Prosecutors believe Entwistle used a .22-caliber handgun that belonged to his father-in-law, then returned the gun to his in-laws' Carver, Mass., home before boarding a plane to England.

"He owed money in London. He did not have a job. He did not have a visible means of support," Coakley said. "He was unable to provide income for himself or his family."

She said it appeared Entwistle concealed his financial troubles from his wife and family.

Rachel's family released a statement through a spokesman Thursday, saying they were deeply saddened at the arrest of Neil Entwistle.

"Rachel and Lilly loved Neil very much. Neil was a trusted husband and father and it is incomprehensible how that love and trust was betrayed in the ultimate act of violence. We are heartbroken at the loss to understand how this happened, but as our pastor, Father McKenzie reminded us just eight days ago, God didn't do this. There is evil among us," family friend Joe Flaherty said.

Neil Entwistle met Rachel Souza, a Kingston, Mass., native, while she was studying abroad at York University in England in 1999. They were married in 2003 and Lillian was born last April.

Watch NewsCenter 5 for continuous live updates on this developing story and refresh this page for new details.