Rookie Officer Kelvyn Vargas nabs teen shooting suspect Tyrell Johnson

A rookie cop is being credited with chasing down a teenage shooting suspect in the Bronx. 
According to police, 17-year-old Tyrell Johnson shot a man four times at a bodega on East 172nd Street Wednesday night. 
They say Officer Kelvyn Vargas heard the gunshots and ran toward the scene, catching and arresting Johnson close by. 
The teen is being charged with felony assault and criminal use of a firearm. 
The victim is in critical, but stable condition.