Police discovered monopoly money in a backpack they believe belonged to the masked assassin who gunned down UnitedHealth CEO Brian Thompson in Midtown, law enforcement sources told the Post.

The colorful play money was found by NYPD detectives inside of a gray backpack hidden in the brush in Central Park on Friday that may be the one the gunman ditched after the shooting, sources said.

The backpack, similar to the one the shooter wore in the caught-on-camera killing, was recovered south of the carousel near Heckscher playground.

In addition to the board game cash, a jacket was also found inside, sources said.

Thompson, 50, was gunned down outside the Hilton Hotel in Midtown just before dawn on Wednesday as he walked to an investor event without any security detail.

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The assassin quickly fled after the caught-on-camera killing, sped through Central Park on a bike and at some point left the city on a bus for Atlanta, according to authorities.

The shooter has evaded law enforcement for four days as the FBI has joined in the massive manhunt. 

This is a developing story. Please check back for updates.