Andrew Flonory and his brother, Dwayne, were headed to a house party on Astoria Street in Mattapan the night of June 18, when a man standing in the home’s yard raised a gun and opened fire, prosecutors say.

Both men were hit, and Andrew, 31, was fatally struck in the head. He died less than a mile from where his 21-year-old sister and her 2-year-old son were killed in a mass shooting in 2010.

On Friday, the man prosecutors say killed Andrew Flonory and wounded his brother was ordered held without bail in Dorchester District Court. ­Julian Troche, 24, of Boston pleaded not guilty to charges including murder, assault with intent to murder with a firearm, and assault and battery with a dangerous weapon causing serious bodily injury.

Troche has been convicted for drug possession with intent to distribute and in 2013 was sentenced to three years in state prison on a firearms charge, according to prosecutors and court records. His lawyer, James Greenberg, said his client “adamantly denies’’ shooting the Flonory brothers.

Flonory’s family members wept as they looked on. They declined to speak to reporters as they left court.

After Troche opened fire, Dwayne Flonory, who was shot in the back and legs, pulled out a gun and fired back, Suffolk Assistant District Attorney Mark Hallal said.

He missed, and Troche ran back into the house party, Hallal said. A second shooter, whom Hallal said authorities have identified, also ran. The suspect has not been arrested.

Dwayne Flonory was able to limp another block before he collapsed.

Troche was identified by a witness, Hallal said, and his cellphone records placed him nearby at the time of the shooting. An official with knowledge of the investigation said the killing seemed to be gang-related.

The Flonory family has faced immense loss. On Sept. 28, 2010, 21-year-old Eyanna Flonory, and her toddler son, Amani Smith, were shot to death by three men on Woolson Street, along with Eyanna’s boyfriend, 21-year-old Simba Martin, and another man, 22-year-old Levaughn Washum-Garrison. It was one of the city’s worst killings in years.

Two men were convicted in the case; a third was acquitted.

Two months before the murders of his sister and nephew, Andrew Flonory was shot multiple times while he waited for a bus at the Red Line’s Ashmont Station in Dorchester.

Troche was arrested Wednesday by the Boston Police Fugitive Unit and SWAT officers as he sat in a vehicle on Burbank Street.

“This is a very dangerous individual with a history of violence taken off our streets,’’ Boston Police Commissioner William Evans said in a statement. “I hope this arrest brings some level of comfort to the Flonory family.’’

Jan Ransom of the Globe staff contributed to this report. Evan Allen can be reached at evan.allen@globe.com. Follow her on Twitter @evanmallen.