THE BRONX - Police have arrested two people in the stabbing of a 19-year-old teen after an argument about a stolen smartphone.

Authorities say the confrontation erupted Saturday when Alex Herald accused 22-year-old Victor Montalvo of stealing his smartphone on a southbound 4 train.

Police arrested Montalvo and his female companion after surveillance video showed him shaking his hand in apparent pain after arriving at a Bronx building following the incident.

Herald is in critical but stable condition.