Illegal Gun Confiscation?

I was not there, but here's what happened, as it was explained to me.

On Dec 31, a friend was going to work, and arrived in his car on campus at D.U.
He has a permit, and carries. D.U. buildings are a no-carry zone, so he takes the
gun, unloads it, puts the gun in his glove compartment, puts the round
from the chamber into the magazine, and puts the mag into his carrier on
his belt.

He thinks someone may have seen him handling the gun and called the police.

He leaves his car, and heads for his destination when he is accosted by
the Denver Police, guns drawn, handcuffed and searched. He produces ID and
permit, tells the police what he did, gets berated for having 2 magazines on him, (too much ammo) has his car
searched, and his gun "found", where he told them he put it. The cop also expressed displeasure at some of the literature he found.

In the end, he's just a citizen with a permit, disarming before entering
a "gun-free" zone, but, since he cannot produce a receipt for the gun,
which he bought about 20 years ago in Texas, the gun gets confiscated.
The cops say he can have it back when he can prove it's his.

I don't know about you, but I couldn't prove I owned my watch (for example) if challenged, and I'd hate to have it wind up in someones collection when the evidence lockers are cleaned out. As to granting permission to the police to search your vehicle, this is a no-win situation. If you agree, there is nothing at all in your car that cannot be construed as evidence against you. If you refuse, the situation becomes the cop equivalent of vaudeville as the in-house judge signs the warrant, the PD demolition team arrives on scene and when they're done you'll be lucky if your car is drivable.

Several people have offered to help on this, and I expect I'll hear more on Monday, but in the meantime this looks like a case of egregious abuse of authority on the part of the Denver PD.