After Kyros called Garp to report the situation, Garp—who had only recently parted ways with Yoriichi and was preparing to return to Marine Headquarters—immediately changed course and headed straight for Water Seven.
After returning from their trip to Shimotsuki Village, Garp had left Yoriichi and the others in Water Seven before leading his fleet back toward Marine Headquarters.
Garp was in his prime and held the rank of Vice Admiral at headquarters. His daily duties kept him extremely busy; there was no way he could stay in Water Seven with Tsugikuni Yoriichi and the others until Tom finished building the warship.
So after dropping Tsugikuni Yoriichi and the others off at Water Seven's docks, Garp had gone off to handle his own affairs.
But unexpectedly, he had barely sailed away from Water Seven when Kyros called him and reported the matter of killing the CP9 leader.
Although Tsugikuni Yoriichi was now also a Vice Admiral at headquarters, making him theoretically Garp's equal, there was no question of one reporting to the other. Still, Yoriichi intended to bring Garp into this matter.
With Garp, that stubborn old bastard, serving as a buffer, Marine Headquarters would probably handle things differently.
That was one of Yoriichi's little schemes.
While Garp rushed toward Water Seven, Yoriichi, accompanied by Kyros and the others, interrogated the CP9 agents. Yoriichi had assumed they were secretly investigating Tom, but the results of the interrogation had nothing directly to do with him.
These CP9 agents had set their sights on the Adam Tree Tom had somehow acquired and intended to swallow it up under the pretext of arresting pirates.
As for why these people had confessed so honestly under Tsugikuni Yoriichi's interrogation, perhaps...
In the hearts of these CP9 agents, they simply did not consider what they had done