Brookfield police described the robbery at gunpoint of several teenagers in the backyard of Brookfield home on July 18 as unprecedented. No one was injured during the robbery, which took place at about 11:20 p.m. in the 3500 block of McCormick Avenue during a party hosted by a teenager whose parents were out of town at the time.

“This has never happened before,” said Brookfield Police Lt. Edward Petrak, who said detectives are actively investigating the incident and are following up on leads.

Beyond that, police declined to elaborate on how they believe a man armed with a handgun picked out a party of unsupervised teenagers in a Hollywood backyard that would not have been particularly visible to anyone walking down the street at that time of night.

According to police, the offender was a black male, about 5-foot-10 with a slim build, who was wearing a mask over his face. He was also wearing a white T-shirt and blue jeans.

A 17-year-old boy who was at the party told police that 10 people, including three adults between the ages of 18 and 27 whom he’d met just three weeks ago, were sitting on a patio and playing basketball in the backyard.

One of the teens was grilling in an area away from the others, closer to the front of the property. At some point, that teen came walking with his hands up, toward rear area of the yard where the others were. Behind him was a masked man, pointing a gun at his back.

A 22-year-old man at the party stated, “This is a joke, right?” The gunman assured him it wasn’t and ordered everyone to get on the ground, empty their pockets and put the contents in front of them, police reported.

Then the gunman allegedly ordered everyone to walk to the back fence of the property, where he reportedly patted them down individually for anything else in their pockets.

After picking up all of the victims’ belongings, principally cash and cellphones, according to police, the offender ran toward the front of the house and headed south to Parkview Avenue where two subjects were seen getting into a dark-colored Chevy Malibu, which sped away toward Washington Avenue.