Allentown, PA – A Pennsylvania father used homemade explosive devices to kill himself, his 2-year-old son, and one of his adult friends, police said on Thursday.

Investigators said that Jacob Schmoyer, 26, mailed four letters on Sep. 29, shortly before he set off a car bomb that killed his son, 2-year-old Jonathan, his friend, 66-year-old David Hallman, and himself, WTXF reported.

The blast scattered body parts and debris over several city blocks, according to CBS News.

Video of the aftermath was uploaded to social media.

Blue Lives Matter will not be sharing the video due to the large number of body parts laying around the scene.

“The scene was probably the most horrific thing I’ve ever seen,” Allentown Police Chief Tony Alsleben told CBS News early this week. “It was a large scene. There was a lot of components involved. There’s a lot evidence, so it’s taking a while to process it.”

“The fire was crazy,” resident Carlos Perodin said, according to the news outlet. “The car was pretty much split in half.”

“All three subjects were inside the vehicle – Schmoyer in the driver’s seat, Mr. Hallman in the passenger side of the vehicle and the baby was in a car seat in the back on the driver’s side,” Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) Special Agent Don Robinson said during a press conference on Thursday, according to NBC News.

Agent Robinson said the explosion was the result of “a couple different types” of “homemade explosives.”

“It’s a miracle that no other bystanders were seriously wounded or killed,” U.S. Attorney’s Office Allentown Chief John Gallagher said during the conference. “What happened here in Allentown on Saturday night was nothing short of a nightmare.”

Schmoyer sent one of the letters to the Allentown Police Department, and mailed the rest to family members.

Each letter detailed his plans and explained the construction of the explosive device he planted near the center console of his vehicle.

The special agent said that Schmoyer was “very unhappy with his life,” and that he “described himself in some negative terms” in the letters.

“He was miserable…He admitted to a lot of criminal acts, he didn’t think it was going to get any better,” Agent Robinson explained. “There was a lot of hatred there, and obviously, some directed at Mr. Hallman and his son.”

“Unfortunately, in these letters, [he described] his intent to take Mr. Hallman and his son with him,” Agent Robinson added, according to WTXF. “

Johnathan’s mother, Jasmine Kerecz, has read the letters Schmoyer wrote, her sister, Shannon Rehrig, told The Morning Call.

“[She] wanted to believe that Jake wasn’t capable of this,” Rehrig said of the grieving mother. “She wanted to believe this was an accident.”

“There are letters stating he had something against autism, which he suspected J.J. had,” Rehrig explained. “He murdered an innocent child. That is evil.”

Schmoyer also had a history of depression, Agent Robinson told NBC News.

His family said he struggled with schizophrenia, and had received treatment in the past.

“It’s sad, sad day for all families, there’s really no way to describe what runs through somebody’s mind when they’re doing this, but we are confident that we have determined who is involved and who is responsible, and that is Jacob Schmoyer,” Agent Robinson said.

Schmoyer’s father, Glenn Schmoyer, told NBC News that he and his son were very close, and that he was “traumatized” when he learned what had occurred.

“He always played with his son and I just have so many good memories of them two together,” Glenn told the news outlet. “My son was a very good man and he would give the shirt off his back to help someone in need. He was never selfish. Things meant nothing to him, people did.”

Schmoyer’s grandmother, Kathleen Pond, said that she was stunned to learn that Schmoyer had killed his child, CBS News reported.

“Maybe in my heart I knew he would do it to himself, but never to J.J.,” Pond said.