CHICAGO (CBS) — Three people were charged with aggravated robbery after a police chase that started in north suburban Evanston ended on the sands of Loyola Beach Thursday afternoon in the North Side Rogers Park neighborhood.

At 4:05 p.m., officers responded to a call of aggravated robbery in the 1700 block of Monroe Street in Evanston, according to Evanston police. A 70-year-old woman was approached by someone with a gun who demanded her purse. Another person in a vehicle pulled up in the alley behind a home and also walked up to the woman. When she started to scream, the two people got back into the vehicle and drove away westbound.

Evanston police officers saw a red minivan driving south in the northbound lanes of North Sheridan near West Touhy, which was believed to be the same vehicle involved in the earlier robbery, Chicago Police said. The van drove away southbound on Ridge Avenue into Chicago and Evanston police stopped the pursuit.

Later, the van was found by officers near Pratt Boulevard and the lakefront, police said. Four people got out of the van and tried to run away. Three boys—ages 15, 16 and 17—were caught by Chicago Police and turned over to Evanston police.

The van they were driving was reported stolen out of Chicago, police said. A pellet gun, which looked like a real handgun, was found in the van.

The three boys were charged with one count each of aggravated robbery. The 15-year-old is from Calumet City and being taken to Cook County Juvenile Detention Center. The other two boys are from Chicago.

Further charges relating to the fourth person who was not caught, as well as possessing the stolen vehicle, are pending, police said.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2016. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)