AZUSA — Police arrested two teenagers Friday after a witness reported seeing them vandalizing a wall with graffiti along San Gabriel Avenue.

A 15-year-old boy was arrested on suspicion of vandalism, while a 16-year-old boy was suspected of delaying and obstructing a peace officer for failing to cooperate with officers’ orders, Azusa police Sgt. DeWayne Eldridge said.

Officers responded to the area of Northside Park about 4 p.m. after a witness called police to report the boys scrawling graffiti with spray paint on a brick wall in an alley to the west of the 1200 block of North San Gabriel Avenue, the sergeant said. An officer arrived within seconds and witnessed the vandalism.

A cash reward of $100 was paid to the tipster who reported the tagging crew-related vandalism, police said. Azusa police began a program early this year which offers $100 rewards to witnesses who report graffiti vandalism, leading to an arrest.

Additionally, Eldridge said, the city seeks restitution from convicted vandals or their parents to pay for the cost of repairing the damage.