Antomar Jones, 19, shown here in an arrest photo from 2011, has been charged with fatally shooting Corey Alexander on Feb. 1, 2012

Antomar Jones, 19, shown here in an arrest photo from 2011, has been charged with fatally shooting Corey Alexander on Feb. 1, 2012 (Baltimore Police Department / February 3, 2012)

City police have made an arrest in a double-shooting Wednesday that killed a 31-year-old man - charging a 19-year-old man who relatives say was part of a youth mentoring program the victim worked with. 

Antomar Jones has been charged with first-degree murder and attempted murder for the shooting in the 5700 block of Nasco Place that killed Corey Jamal Alexander and injured a second 31-year-old man. Police say Jones was in the backseat of a car in which Alexander was a passenger, and he shot both men during an argument. 

Police did not say what sparked the argument, and could not confirm the relationship between Jones and the victims. But Alexander's sister, Stacie Alexander-Price, said the surviving victim told them Jones was involved in a youth program that Alexander worked for as a mentor.

"It's just unexplainable," said Alexander-Price. 

Alexander had no criminal record; he was a City College graduate who had worked for the Postal Service and recently graduated from Coppin State University with a degree in business management. Family friend David Miller, of the Urban Leadership Institute, called Alexander was a "role model for young men."

"When the doctors told my mother that he didn't make it, she was on the floor. I've never seen my mother like that. I was numb all day," Alexander-Price, 40, said. "The people coming through the house yesterday, they were young people leaving work or coming from school. None of them can understand why something like this could happen."

The surviving victim, who has not been identified, remains hospitalized.

Jones' grandfather, meanwhile, said he was shocked by the charges. "This isn't a troubled kid," said Fred Watkins, who said Jones graduated from Mergenthaler Vocational-Technical High School. "This boy had good potential. Me and his grandmother, we did everything we could, we just couldn't afford to send him to college. I wish we could."

Jones had been arrested before, charged with drug possession last fall and with assault in 2008, though both cases were dropped by prosecutors. 

Watkins said police came to his home this morning looking for Jones, who lives with his father. 

"I'm sitting here bewildered; I don't know what this is about," Watkins said.