Power is current x voltage.
A clamp meter measures the amps flowing through the speaker wire. Voltmeter for the voltage. Multiply the numbers and boom, "I've got the power".
Here is my 2k watt amp driving a 12W7 near full tilt. About 930 watts.
Trust pop the information is out there on him from multiple search engines and other car audio forums. Whether or not there is a police report is irrelevant not with how many people saw things at competitions along with other information.