New Castle County police released a picture of the memorial that had been defaced with red spray paint.
Police say it was vandalized sometime over Labor Day Weekend.
The memorial was dedicated to Lt. Joseph Szczerba, who was killed in the line of duty nearly 13 years ago.
On September 16, 2011, Szczerba was fatally stabbed while trying to arrest a suspect.
After the 44-year-old's death, people around the community decided to honor him.
"I wanted everyone to see it as they drive by. I wanted everyone to remember what happened," said Paul Van Vechten, the man who created the vandalized memorial.
"My neighbor found out what I was doing and offered to help pay for it," he recalled.
Vechten first discovered the vandalism Monday morning. He said the memorial was scrawled with derogatory comments.
"I just happened to glance over and saw someone happened to paint graffiti over it," he said.
He and several officers worked on Labor Day to clean it up.
"The plaque says it all about the life he led, the commitment he made, and the sacrifice he paid," said Kathy, Szczerba's widow.
Szczerba's family has been known to visit the plaque, which means a great deal to them.
"One year his family, his uncles and stuff, they were so appreciative, they gave me a Christmas card and wrote a note in it about how much it meant to them," said Vechten.
Every year on September 16, residents in the area come together around Vechten's memorial to honor Szczerba.
"We come out here on the 16th, shortly after midnight to celebrate and to remember him," said Colonel Joseph Bloch with New Castle County police.
Sadly, this year the plaque is no longer hanging.
Despite this, there are reminders of Szczerba and his legacy all over New Castle County. The police academy is named after him, and so is a local park.
Now, investigators are asking residents to review their surveillance footage in hopes of finding the suspect.
"If you see anything, any time between August 31 at 8 a.m. to about 9:30 on Monday," said Sergeant Andrea Botterbusch.
Police say this incident is one they'd like to find closure to, as it hits close to home.
"I'd like to believe whoever desecrated this sign didn't know Joe because if they knew the kind of person he was and the kind of human he was they wouldn't have damaged it," said Bloch.
Anyone with information should contact the police.