The deadly Saturday night car explosion in Pennsylvania that killed three people, including a two-year-old boy, was a targeted murder-suicide by a “depressed” father, authorities announced on Thursday.

“It is the collective assessment and opinion of the entire investigative team that this was an intentional act,” Don Robinson, a special agent for the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, said at a news conference.

Authorities said Jacob Schmoyer killed his son, Jonathan, and 66-year-old friend David Halman on Saturday afternoon after Schmoyer detonated a homemade explosive device inside his car.

Shannon Rehrig, the toddler’s aunt, told The Daily Beast on Thursday that her family is “disgusted” by what happened.

“I have nothing to say about that evil man who murdered my nephew,” said Rehrig, who is the sister of Jasmine Kerecz, the boy’s mother. “We are not good.”

The announcement comes after it was revealed that Schmoyer sent suicidal letters to family and local police. According to officials, the notes “indicated a desire not to stick around” and his plans “to take Mr. Hallman and his son with him.”

“He was miserable. Basically, the four letters describe a miserable life, he was unhappy himself,” Robinson said. “I don’t know if shame is too strong of a word because of what he did later, but he admitted to a lot of criminal acts, he didn't think it was going to get any better. There was a lot of hatred there, and obviously, some directed at Mr. Halman and his son.”

“It’s a sad day for the family,” Robinson said.

The Allentown Police Department said the 26-year-old sent four letters, three to family members and one to the police. The first letter was received on Tuesday, and another three the following day which also detailed the materials used in the device, Robinson said. Authorities admitted they are still trying to confirm the authenticity of the letters but they believe all are from Schmoyer.

In the letters, he also confessed to additional crimes, Robinson said, including petty theft and burglary.

“It’s a miracle no other bystanders were seriously injured or wounded in this,” said Assistant U.S. Attorney John Gallagher, comparing Saturday’s explosion to a “war zone” and “a nightmare” where emergency staff had to work long hours for five days.

“This was an individual who intentionally set out to commit suicide, and do it in the most violent and destructive way that he could conjure up,” Gallagher said.

Following the detonation, graphic videos of the blast’s aftermath appeared on social media, showing body and car pieces strewn about the ground near the burning vehicle.

Residents in the blast zone were allowed to return to their homes Wednesday night, police say, adding that some homes were so heavily damaged by the explosion that families might not be able to return for a few days.

Thursday's press conference also revealed that Lehigh County Coroner Scott Grim has not yet ruled a homicide, but has concluded all three died of traumatic injuries.

Gallagher and Robinson did not established an official motive for targeting the friend with the explosion, but revealed it was created using two separate devices and that Schmoyer did “lure” Hallman out.

This belief, Robinson said, stems from where the bomb was located: Either in the center console of the vehicle or near the passenger seat.

“We are confident Schmoyer acted alone. He is not involved in any groups,” Robinson said. “We are confident this was an isolated incident.”

According to local newspaper The Morning Call, a security video shows Hallman getting into the passenger seat of the car with Schmoyer and his son. Two seconds after Hallman shut the door, the car exploded.

Jasmine Kerecz, the mother of Schmoyer’s son, told the The Daily Beast on Thursday she “has nothing to say this time.”

Schmoyer’s family, on the other hand, struggles to understand how this all happened.

“[He was] a wonderful father, brother, son, boyfriend, cousin, nephew, grandson, great-grandson, and soon would have been an uncle as well,” Tina Schmoyer, his sister, told The Daily Beast. “Someone whose heart was always for others and would give the shirt off his back to anyone in need.”

“This is who my brother was,” Schmoyer added. She provided The Daily Beast with the above image of her brother holding his newborn child.