There were two ways to verify which situation it was.
The first was to continue looking back by checking earlier surveillance footage.
The second was to check the surveillance footage from after the incident until now. If the cameras caught someone coming down from the roof who hadn't gone up there before, that person would be the killer, and they could simply issue a warrant for their arrest.
If no such person was captured on camera,
Then perhaps the killer was someone with exceptional patience, likely still lying in wait on the rooftop.
In that case, they would only need to check the Guojin Building to confirm.
If the killer had indeed used this method, they should still be hiding on the roof, and could be caught immediately upon arrival.
Conversely, if no one was on the roof, then Xu Mo had guessed wrong about the killer's method.
With this in mind, Xu Mo began reviewing the surveillance footage from after the incident until now.
This segment was relatively short - the incident occurred around eight in the morning, and it was now ten-thirty at night, spanning just over ten hours.
It only took Xu Mo ten minutes to review all the surveillance footage from the stairwell camera from after the incident until now.
Because people were generally wary of death-related matters, no one had gone up to the roof after the incident - not a single person from then until now.
In this footage, no one had gone up, and no one had come down.
As usual, worried about missing something, Xu Mo reviewed it a second time.
After another ten minutes, Xu Mo finished watching the footage again.
The results were the same as the first review.
Given this situation, they needed to verify things at the Guojin Building.
Since the stairwell cameras hadn't captured the killer leaving the roof after the incident, either they were still hiding up there, too afraid to come down, or they were never on the roof at all, meaning Xu Mo had guessed wrong about their method.
Xu Mo called Han Fei back.
"No need to keep watching, Captain Han. I've gone through the footage from forty-eight hours before the incident until now twice, and haven't found any suspicious individuals. Either the killer has incredible patience and waited more than forty-eight hours to commit the murder, in which case they should still be hiding on the roof, or I guessed wrong about their method and they're not hiding up there at all. I'm heading to the Guojin Building to check."
Han Fei: "???"
"You've finished? You've even reviewed all the footage from after the incident until now??"
Han Fei was bewildered, his mind struggling to process this information.
Originally, he had been intently focused on the surveillance footage, afraid to even blink too much for fear of missing a clue, which had left his eyes strained and head slightly swollen.
Even watching at six times normal speed, he had only managed to review twelve hours of footage, barely half of what he needed to see.
Yet Xu Mo was telling him he had already reviewed forty-eight hours of pre-incident footage up to the present, and had done so twice!
It had only been about two hours since they started reviewing the footage.
At six times speed, Han Fei had only managed to watch twelve hours of content.
While Xu Mo... had somehow reviewed forty-eight hours of pre-incident footage up to now! And twice at that!
The footage from forty-eight hours before the incident until now was at least sixty hours, and watching it twice meant one hundred and twenty hours
Xu Mo had watched one hundred and twenty hours of footage in just two hours? At sixty times speed???
So Xu Mo's viewing speed was ten times his own?
Was this even humanly possible?
"I've finished watching it twice, and I'm certain I didn't miss anything," Xu Mo replied. "I'm heading to the Guojin Building now to check."
...
After ending the call,
Xu Mo went directly to the Guojin Building.
Han Fei continued watching the surveillance footage.
Although Xu Mo claimed he had reviewed all the footage and was certain he hadn't missed anything,
Han Fei didn't believe it.
How could anyone review sixty hours of footage in just two hours? And watch it twice?
Sixty times speed... that was ridiculous! It was clearly just Xu Mo bragging.
The bragging itself wasn't the issue, but the claim was just too outlandish!
Watching at such speed, how could he possibly catch anything? Even if there was someone suspicious, Xu Mo probably wouldn't have noticed!
Han Fei believed he had to rely on himself.
Xu Mo's claim was simply too incredible - he would never believe someone could review that much footage without missing anything in just two hours.
So he completely ignored Xu Mo's words and continued watching the footage.
...
While Han Fei continued reviewing the surveillance footage,
Xu Mo had already driven to the Guojin Building and headed straight to the roof.
After walking through the rooftop stairwell door, Xu Mo turned and looked up at the top of the structure.
From this height, he couldn't see if anyone was up there.
To know if someone was up there, he would need to climb up and look.
Xu Mo backed up a few steps, then started running.
Just before reaching the wall, he kicked off it forcefully, using the momentum to grab the ledge with both hands, then used his arm strength to pull himself up.
Once his eyes cleared the ledge, Xu Mo could see the entire roof area above the stairwell.
There was no one there.
Xu Mo let go and jumped down.
No one up there - had he guessed wrong? Was this not the killer's method after all? Xu Mo furrowed his brow.
He mentally reviewed what they knew.
He had watched all the surveillance footage from forty-eight hours before the incident until now, found no sign of the killer, and now found no one hiding on the Guojin Building's roof.
Therefore, the killer hadn't been to the roof at any point from forty-eight hours before the incident until now!
If they hadn't been there, how had they committed the murder?
Xu Mo felt puzzled.
How could the killer have murdered someone without any contact? Could they kill from a distance?
This didn't make sense...
Or... were these really just three ordinary suicide cases?
That wasn't right either - this couldn't possibly be suicide!
Others might not know, but Xu Mo did. With his Conan-like intuition, every case he encountered had something suspicious about it. There was no way these were suicides.
Just as Xu Mo was pondering this, he suddenly witnessed something happening on the roof of the building opposite.
A man with an anguished expression was slowly walking toward the edge of the roof, apparently preparing to jump...