By Kim Glovas and Oren Liebermann

PHILADELPHIA (CBS) - Police arrested two young men Friday evening on charges of institutional vandalism after they defaced the Vietnam Veterans Memorial at Penn’s Landing.

Terry Williamson, who is the president of the Philadelphia Vietnam Veterans Memorial Fund, explains what happened.

“Our custodian, Jim Moran, caught two young men skateboarding inside the memorial, defacing the granite and causing other damage. We estimate it will be in several thousand dollars worth of damage.”

Moran pointed out that there are signs at every entrance that make it clear skateboarding is prohibited and said this never should have happened.

“Our young men and women are coming home with flags draped over their coffins and here these two, stupid thugs come in here and jump all over the memorial.”

This latest incident occurs a little more than two weeks after Councilman David Oh introduced an ordinance to City Council to increase penalties for this type of crime.

Williamson said the monument has been vandalized dozens of times since it opened 25 years ago.

An effort is currently underway to raise $500,000 to open the Spruce Street side of the memorial. This would make it easier for police to monitor the site.