Grammys producers have stepped up security for Sunday’s awards ceremony as Los Angeles police hunt for a man suspected of killing three people this week.

Former Los Angeles Police Department Officer Christopher Dorner is thought to have fatally shot three people including one police officer early Thursday.

The suspect sent a package to American news anchor Anderson Cooper that included a manifesto vowing to take revenge on those he believed got him fired from the force.

Included in the document were references to celebrities including Charlie Sheen and Ellen DeGeneres.

As RadarOnline reports, Grammy bosses are concerned about his fascination with celebrities and have amped up security for the Los Angeles awards ceremony as a result.

“There will be uniformed and plain-clothed police working in and around the Staples Center because Christopher Dorner is still out there,” a source told the website.

“Police are being extra vigilant, especially as Dorner’s manifesto mentioned several celebrity names, including some possible guests at this year’s Grammys.”

There was no indication of a direct threat at the event but Grammy Awards producers and police are said to be taking every precaution to keep guests safe.

A manhunt is ongoing in California, Arizona, Nevada and Mexico for the suspect.

Downtown Los Angeles is meanwhile gearing up for the star-studded ceremony, with performances expected from Miranda Lambert and Dierks Bentley, Taylor Swift and Carrie Underwood, fun., Mumford & Sons, Elton John, Ed Sheeran and Justin Timberlake.

The SexyBack singer is making a comeback with his new single, Suit & Tie, from his forthcoming album, The 20/20 Experience.

It will be Justin’s first time performing at the Grammys in four years.