Murdering at the school

The recording

The day started normally. Frank woke up at 7:00 a.m. and had a shower. Then he dressed up and went to "check" if Kyle was less sick just to convince is wife that he was sick. He got out of the house and entered in the car. He was very nervous, but he could hide it. When he finally reached the police department, he saw Charles smoking at the entrance.
"Are you ready?"- asked Charles
"I think so"- answered Frank
They entered the delegacy and sited down on their chairs.
It passed an hour and Frank finally was ready for the conversation with Percy .
He knocked Percy's office door.
"Get in"- said Percy
"It's me"- said Frank
"Oh, hi mr Frank!"- said Percy- "Why are you here when you should be at work?"
10 minutes later Frank got out of the office. He sited in his chair, and whispered to Charles:
"I've got the tape"
Then Charles called the police without anyone notice. Just 2 minutes later the cops were there.
"POLICE! EVERYONE IN THE GROUND!"- said one of them
"What's going on?"- asked Percy to the cops
"WHO CALLED US?"- asked a cop
"I did!- answered Charles, pointing to Percy- "This man is a criminal!"
Then, Frank showed the tape to the cops while Percy was panicking.
When the tape ended Percy was moved to a police car while shouting:
"SOMEDAY I WILL GET MY REVENGE FRANK!"
"You herded that tape!"- said Charles to the cops- "We have no time to lose! Our next stop is Valsassina school!"