Jo's father was supposedly killed while on a hunt with John Winchester as Demon possessed Sam told her, that John actually killed Bill to "put him out of his misery" after being fatally wounded, despite Bill's pleas to see his wife and daughter one more time. But hey, demons lie.

William Harvell just wanted out of hunting but John convinced him to go on one last hunt, trying to change his friend's mind, if he stopped hunting bad st*t was gonna follow. It was on this hunt that Bill nearly died, John did basically leave him for dead, though he didn't kill him directly, it was then an angel came to him. I know you're wondering, why would a hunter let an angel possess him? Good question, Balthazar promised that Ellen and Jo would be safe. That's really why he unsung the Titanic so somehow Ellen and Jo wouldn't die.

Ellen did know the truth, that it was John's recklessness that got her husband killed. All William wanted to do was retire from hunting and help raise his little girl. He wasn't getting younger, he had been 44 when Jo was born, and he wanted to live to be able to walk his daughter down the aisle someday, something Will's own father wasn't unable to do with his daughter (Bill was brought up with a family of hunters and his older sister had been killed by their father's work that had followed him home.). John had convinced him to go on one last stupid hunt, a hell spawn, the one thing Will never hunted before. He couldn't turn up the opportunity.

She did not know the details of his murder, but she knew John Winchester did not put him out of his misery. He just left the man, he called his friend, for dead. She knew the truth, that John Winchester was a coward. She would forever blame him, but not his boys, though she had at first, trying to convince herself they were no different from John but they weren't their father at all.

John Winchester lied in his journal how William Hervelle had died, as if somehow putting his friend out of his misery excused the fact that he was a coward. It looked like smoke and sounded like a million flies. Bill looked down from the stars just in time for it to flow right into him. He started jerking like a condemned man in the electric chair, and two voices were coming out of his mouth. One was the thing, the hellspawn. I don't know what language it was speaking, but its voice was horrible. It was the sound cancer would make if it could Bill, he kept saying over and over again, "John, shoot me, shoot me, John."

So I did.

It was the worst mistake I ever made. It was careless and stupid and it got a good man killed. A husband and father, and a damned good hunter, and I don't know how I'm going to explain this to Ellen. And Jo, poor Jo. She's four years old. How am I going to tell her? I can't just let Ellen do it. I'm responsible. It was over in less than a minute, Bill Harvelle dead and me standing there with a gun in my hand listening to the echo of the gunshots in the hills and the echo of the awful hellspawn voice in my head.

John's entry conflicted with two things.

According to Jo, "Our dads were in California: Devil's Gate Reservoir. They were setting a trap for some kind of Hellspawn. John was hiding, waiting, and my dad was bait... The thing showed up. John got too eager, jumped out too soon, got my dad exposed out in the open. The thing turned around and killed him."

Meg's version of the story, "You see, Bill was all clawed up. Holding his insides in his hands. He was gurgling and praying to see you and Ellen one more time. So my dad killed him. Put him out of his misery like a sick dog. (singing) My daddy shot your daddy in the head." This was partially a lie of course.

The thing had torn through him, leaving him laying there, his insides exposed.

"oh,

"It's...okay. I can make it." He didn't seem aware of how extensive his injuries were.

You're not going to. Voicing his thought, John shook his head.

If he tried to move him his entrails would likely fall out and if they got to the Impala with no problem, there was no doubt that Bill would bleed to death before they reached the nearest hospital.

In the end John only saw two options,

1. Leave him to die.

2. Put him out of this misery.

John raised his gun, pointing it at Bill's head.

"Do it." It wasn't a desperate plea, it was more of a challenge at first, and just rightfully so. "Ellen and Jo will understand." But John couldn't bring himself to shoot his friend. He thought of his own boys and thought if the situation was in reverse he would want Will to just leave him. "John, shoot me." The William Harvelle, John Winchester knew would never beg. But now, he was begging, and in excruciating pain. One of the bravest, greatest hunter's he's ever met, was re, He couldn't just stand and watch him suffer, he couldn't pull the trigger either.

"Shoot me. John."

John lowered the gun to his side.

"Please."

"I'm sorry." He said, and simply walked away.