Halifax Regional Police have two teenagers in custody and are looking for more people after a brazen daylight shooting on a Metro Transit Bus in Dartmouth on Thursday afternoon.

Police said the number 72 bus was carrying seven passengers on Pinecrest Drive when a fight erupted among three passengers.

Mike Falconer was driving by the bus at the time.

"From the outside it looked like two people inside beating on one person and then I heard a shot. I saw two other people come flying out of the bus and take off," Falconer said.

Const. Pierre Bourdages said the call came in just before 1 p.m.

Police were on scene in minutes swarming the area with a search dog and officers, including the footpath through McCullough Park

Police said a 16- or 17-year-old boy with a slim build and a tattoo on his collarbone left in the company of a 16- or 17-year-old girl with dark hair and a red coat.

Another 16- or 17-year-old boy with blue eyes, short spiked hair and a tattoo across the front of his neck also fled the area.

They would not say which male they have in custody. A second man, aged 18, was arrested overnight and is due in court Friday.

The bus driver has been relieved of duty and Metro Transit said it has offered him counselling.