Police say two teens who robbed two women - and pistol whipped one of them - near Ashmont station early Sunday were arrested not long after when officers activated the tracking app on one of the phones.

The Boston Police Department reports the teens, one male, one female, both 17, attacked two women around 1:10 a.m. on Alban Road. They beat one in the head with a gun and took their phones and a purse before jumping on a trolley to Mattapan, police say.

"Using the 'Track My iPhone' app from one of the officers' cellphones, the officers and the victims were able to track one of the stolen phones to the area of Bushnell and Van Winkle Streets, where the phone appeared to be traveling along the path of the MBTA Red Line trolley route toward Mattapan Square.

Officers met the trolley in Mattapan Square, police say:

"As they boarded the trolley entering the station, observed two suspects fitting the broadcast descriptions carrying the victims' property. Officers performed a pat frisk of the male and recovered a black painted air-soft gun in the suspect's waistband. Both suspects were positively identified, and officers recovered all of the victims’ stolen property."

The victim who was beaten was taken to a local hospital for treatment.

The teens were both charged with being delinquent for armed robbery, assault and battery by means of a dangerous weapon and receiving stolen goods.