A Massachusetts YouTube bodybuilder whom police spotted outside a home, as he was on top of a woman and repeatedly stabbing her, suddenly died after being tased and arrested Thursday night.

The man, identified as Erich Stelzer, 25, of Cohasset, reportedly died on the way to a hospital after police used a stun gun in an effort to subdue him, Norfolk District Attorney Michael W. Morrissey’s office said in a statement Friday.

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His victim, 24-year-old Maegan Tapley, reportedly suffered “extensive stabbing and slashing injuries" and is being treated for severe injuries. She's likely to lose an eye due to the injuries, police said.

In a statement to NBC Boston, the woman's mother, Susan Tapley, said her daughter will recover from the ordeal, though may need specialists' help.

"She's going to mend, she's going to be alright ... it's going to take time to recover. She'll need plastic surgery and an eye specialist," she said.

"I feel for [Steltzer's] mother," she added. "She just lost her son. My daughter almost died because of his lunacy."

Authorities did not reveal the motive for the attack.

During the attack, Stelzer apparently acted bizarrely and may have suffered from a "possible mental health issue" or an "altered mental state," according to WBZ-TV source.

Fred Siegel, a neighbor, told the local station that "It’s unfortunate you never want to see anybody get hurt and you certainly don’t want to see someone die over something," adding that "It’s unfortunate that it happened and who knows why it happened."

"It's a really sad thing," neighbor Ian Lyster told the Patriot-Ledger of Quincy, Mass. “It’s really good police were able to stop it right before the woman [could have been] killed.”

Stelzer had met the 24-year-old woman via the Tinder dating app, FOX affiliate Boston 25 News reported.

Cohasset police arrived at a Church Street house after receiving a call about a “disturbance” around 10 p.m. Thursday, the FOX station reported.

The police officers handled the case properly, Cohasset police Chief William Quigley told the Patriot-Ledger of Quincy, Mass.

"I’m proud of the work that the officers did,” Chief Quigley said. “Although it is very sad that someone lost their life, my officers did a great job given the circumstances."

"I’m proud of the work that the officers did. Although it is very sad that someone lost their life, my officers did a great job given the circumstances." — Chief William Quigley, Cohasset police

A source told the FOX station that Stelzer lived with his mother, who had been concerned about her son’s mental health.

Stelzer's father, meanwhile, went to Facebook to accuse the police of not telling the full story about his son's death. "My son. Killed by cops. Here comes the cover up," wrote Harry Stelzer, attaching a picture of his son when he was young.

"There was a [violent] confrontation at his house last nite,” the father wrote in another post on Facebook. “Police came and tased him 4 times. 4 times. He died on the way to the hospital. 25 years old. He was my life. This is not over. Let me bury my dead and then the show begins. Rest In Peace my son. Love you for ever. I am hurting.”

Authorities said an autopsy will determine the cause of Stelzer’s death. The investigation is continuing, the district attorney’s office statement said.