-Short Version:

Joseph stopped and turned his head to look up at the empty space directly in front of him in shock, terror and dawning understanding. Suddenly, he knew the answer. He was already dead and only just learned it. The pieces fit together within his mind, a side product of years knowing his trickster brother in law. Then again, even he might have been impressed by the preparation, the cunning and the execution.

It was so easy to see. First, when he was on the fire escape up above them he would drop the arrow into position, then deliberately lure him away to this location. Afterwards he would hide in a corner, away from the trap while his Stand did the work. It was a Stand that could not be attacked, with even other Stands passing through it as though it was a shadow. Therefore, Lonely Heart’s heart bullets simply passed clean through. This determined Painted Black’s position and allowed for the trap to work the way it did so neatly. That position was vital to the plan, absolutely integral. What was more, the boy must have willed his Stand to talk on his behalf, taunting Joseph’s failure to land a killing blow while luring him into striking out again and again until he sealed his own doom. Those taunts served a second purpose as well beyond the psychological, hiding the strange noise that Joseph would have heard, yelling a one word taunt to keep Joseph from noticing that the sound the heart bullets made when they stopped was not that of tearing flesh or struck bone or anything like a human body being hit by a projectile.

But instead the sound of them shattering into some of the bricks that made up the wall that was even now falling apart on top of him.

At most he had a few seconds to react. Time seemed to slow to a crawl, and Lonely Heart whipped around into action to fire off a shot into a segment of descending death. The brick shattered into three pieces, and each of them continued on its own trajectory. There were too many targets all at once. Too little time to protect himself from them all.

-Lulu's Bizarre Adventure Chapter 18(b)

-Long Version:

“You can’t escape!” he yelled. “Your invisibility cannot help you! My Stand can sense your every move, no matter what you do! No more tricks! No more distractions! Your leg is injured, you cannot run far! Stop, and face me!”

Ah! It seemed as though he had stopped to rest just around the corner! Joseph’s suspicions flared up immediately, common sense stepping in over his fury to warn of a trap. The warning was not heeded. What trap could he set? What weapon could he bring to bear? Anything he tried to wield would have to move to have any effect. A rope around his ankle? He would have Lonely Heart cut it with a bullet. A projectile? A blunt instrument? Easily detected, easily deflected! While it was true that there were such things as “weapons that do not move” within this world, such as pit traps and the like it would not be possible for the boy to set these up so easily. Nothing like that lay available to him, and so Joseph stepped around the corner, and gaped at the ground just behind where the boy was standing.

“The arrow!” he breathed, stepping into the alley. “So. You did have it after all. If you truly intended to keep this power out of evil’s hands, you would have destroyed it rather than keep it.”

“Hmph,” the boy shrugged. “If you want it back so badly, you’ll have to get by me first. But I’ll warn you, I’ve figured out how your Stand works. Your attacks will no longer have any effect on me at all. You see? All healed already.”

To Joseph’s amazement, the boy stood up and began to jump around as though his leg wasn’t even injured. This boy! Could his ability be the same as - No! Surely not! “You’re bluffing!” he roared, sending a heart bullet directly into the boy’s own twisted black heart. The bullet struck - To absolutely no reaction.

“I told you, didn’t I?” the boy said. “It’s really quite simply a matter of ‘timing’. Your heart shaped bullets, the shape of your Stand… These are clues to its true nature. Your attacks come out at the same rhythm of your own heartbeat! And I will use this fact against you, before I head off to butcher your family!”

“Stop talking nonsense!” Joseph yelled, releasing another flurry of attacks. The boy dodged and weaved, left and right but every bullet hit its mark. Not necessarily a lethal blow each time, but an arm, a hand, a leg, a shoulder. Surely that should have been enough? The heart bullets were hitting each time, but to absolutely no effect! Joseph’s heartbeat rose as images of Joanna and Shirley at this person’s - At West’s mercy and the fear drove his heartbeat on faster, faster, faster still! Each new heartbeat sending more further projectiles, further expressions of his love for his family careening into that invisible body!

“I told you,” the boy laughed. “Useless! How can a person like you keep their family safe from harm? Useless!” another shot struck, deep into his elbow. He continued to laugh. “Useless!” Another shot, into the knee to no avail. “Useless! Useless! Useless!”

But Joseph was not idle in this. While his Lonely Heart attacked and the invisible boy laughed off his strikes and taunted him he was marching forward while reaching for the gun he had been forced to take with him, “in case of an emergency” as West had put it. Obviously, the second he put it against his own head Werewolf would possess him, and he thought there was no other call to use it. Using it to point directly at the invisible boy’s head with tears in his eyes and his heart ready to explode, that was never a scenario that occurred to Joseph at all.

“Who is useless?” he asked. He wasn’t much of a shot, but at this range he couldn’t miss. The boy lunged forward in what appeared to be a desperate act for escape, but in truth served merely to force Joseph’s hand once and for all. He pulled the trigger and expected to feel something more from the experience. Dread. Power. Compared to Lonely Heart, it was nothing at all. He felt the bullet fly out of the chamber, striking at the boy in the middle of his forehead.

Then he felt it continue without the slightest trace of resistance until it stopped and hung in midair about a foot behind the boy, suspended in place by absolutely nothing at all.

“Useless,” the boy uttered, then he melted into the ground and Joseph cursed himself for not seeing it sooner. His Stand! It was as intangible as a shadow! It made sense considering what had happened previously in the battle: If he could attack using his Stand while making it invisible to other Stand users, then he would surely have attempted to do so. Painted Black glid very quickly along the ground, no doubt intended as another distraction from the boy’s true location.

Except… Why do that at all, and then leave? Why did the bullet’s motion arrest so suddenly, and if Painted Black was truly intangible then why had his heart bullets also stopped when they struck?

Joseph stopped and turned his head to look up at the empty space directly in front of him in shock, terror and dawning understanding. Suddenly, he knew the answer. He was already dead and only just learned it. The pieces fit together within his mind, a side product of years knowing his trickster brother in law. Then again, even he might have been impressed by the preparation, the cunning and the execution.

It was so easy to see. First, when he was on the fire escape up above them he would drop the arrow into position, then deliberately lure him away to this location. Afterwards he would hide in a corner, away from the trap while his Stand did the work. It was a Stand that could not be attacked, with even other Stands passing through it as though it was a shadow. Therefore, Lonely Heart’s heart bullets simply passed clean through. This determined Painted Black’s position and allowed for the trap to work the way it did so neatly. That position was vital to the plan, absolutely integral. What was more, the boy must have willed his Stand to talk on his behalf, taunting Joseph’s failure to land a killing blow while luring him into striking out again and again until he sealed his own doom. Those taunts served a second purpose as well beyond the psychological, hiding the strange noise that Joseph would have heard, yelling a one word taunt to keep Joseph from noticing that the sound the heart bullets made when they stopped was not that of tearing flesh or struck bone or anything like a human body being hit by a projectile.

But instead the sound of them shattering into some of the bricks that made up the wall that was even now falling apart on top of him.

At most he had a few seconds to react. Time seemed to slow to a crawl, and Lonely Heart whipped around into action to fire off a shot into a segment of descending death. The brick shattered into three pieces, and each of them continued on its own trajectory. There were too many targets all at once. Too little time to protect himself from them all.

-Lulu's Bizarre Adventure Chapter 18(b)