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.

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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.

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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.

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