By Ian Bush

PHILADELPHIA (CBS) — Police charged one 15-year-old boy in connection with the murder last Thursday of a man walking his dog in West Philadelphia, and a second 15-year-old, the alleged triggerman, surrendered to authorities early Friday morning.

Brandon Smith is under arrest, charged in the murder of 51-year-old James Stuhlman. Tyfine Hamilton, 15, turned himself into police Friday morning.

Hamilton, of the 2100 block of North Wanamaker Street, is a freshman at Overbrook High School, and is said by investigators to be the shooter.

Police have charged Smith with murder and‎ robbery, and he is being charged as an adult.

Homicide Captain James Clark says a 14-year-old is also is caught up in this case. Police say he was arrested in connection with the murder and is cooperating. He is charged with robbery as a juvenile.

Clark said Stuhlman took his dog out for a walk at about 9 p.m. near his Overbrook home. Stuhlman, Clark said, usually walked with his daughter, but he told her to stay home because it was too late.

Clark says the boys were playing basketball when they decided to rob someone. They passed on one person walking a dog in favor of Stuhlman, their chosen victim, apparently because he looked older.

“He was a lot older than the first potential victim and as they stated, his dog looked “weak” or “soft,” Clark said.

Clark said Stuhlman was confronted by the teens and there was a brief struggle.

“At one point, he did plead for his life. He said ‘please don’t shoot me’ … and they still shot him one time,” Clark said.

Stuhlman was shot once in the chest and died. The teens, police say, made off with nothing.

Investigators said both Smith and Hamilton had prior arrests for robbery.