Information developed by Glendale and Phoenix police detectives led them to a vehicle that was believed to be associated with the crimes, according to Glendale police Sgt. Jay O'Neill.
Detectives began surveillance on the vehicle and served a search warrant on two apartments near Glendale and 67th avenues on Tuesday.
O'Neill said the PT Cruiser that was originally identified as the suspect vehicle in these cases was located at the apartments, along with property belonging to the victims.
Ruben Torres, 36, two 17-year-old males and a younger teen were arrested. O'Neill said the 17-year-olds are being charged as adults. The suspects face numerous charges of robbery, attempted robbery and aggravated assault.
Police said Torres and the three juveniles are suspected in five different cases involving eight victims in Glendale and four cases involving seven victims in Phoenix.
A stock, silver Chrysler PT Cruiser was described at the scene of four violent armed robberies that occurred on April 9.
In the first one, a man was stabbed in the area of 63rd Avenue and Mountain View Road in Glendale at about 10 a.m. He sustained serious but not life-threatening injuries.
About 30 minutes later, a man was robbed at knifepoint near 89th Avenue and Camelback Road.
A short time after that, police responded to the area of 37th Avenue and McDowell Road where two juveniles were robbed at knifepoint and one of them was stabbed.
In the afternoon, a man was robbed at knifepoint after getting off a city bus near 35th Avenue and Bethany Home Road.