Police say these cases will remain unsolved unless they get the public's help.
It's been almost a year since the corner of 77th Ave. and 64th St. in Hyde Park was covered in crime scene tape. Brandon Perry, 17, was shot dead on his front porch as he and his sister were commemorating the death of their father, who had died exactly a year earlier.
"Using an assault rifle the suspect began to shoot in the direction of the victims," said LAPD Captain Nancy Lauer. "The group could not flee inside the house because of a broken doorknob and were essentially trapped on that front porch."
The shooting happened on August 22, 2010, and police have not made any arrests.
At a Thursday news conference, city officials announced a $75,000 reward for information leading to the arrest of the man who killed Perry and seriously wounded his sister.
Perry's mother spoke about the tragic night Thursday.
"It was the one-year anniversary of my husband's death. We thought we had made it past that and then Brandon's murdered, slaughtered," said Donna Perry. "His sister shot, and she's in the hospital asking where is her brother. I have to act like he's still living. I've never lied to my children, ever."
Thursday, police released s composite sketch of the man that walked up to Perry's porch and opened fire.
"We have witnesses," said LAPD Detective Colin Braudrick. "We have a way to close this case. We just need a suspect to look at."
At Thursday's news conference, the LAPD asked for the public's help in two other unsolved murders in South L.A.
Local businessman Alonzo Ester was shot and killed on May 13. Investigators say he had just pulled into his driveway on the 4200 block of Hillcrest Dr. when a gunman walked up and opened fire.
The third case happened on August 1, 2010. Police say Ronald Reeves was murdered as he stood on the front porch of his house on the 9500 block of South Holmes St.
"We desperately need the public's help to solve these cases," said Lauer.
Police don't think that these shootings are related even though some of the circumstances are very similar.
Anyone with information related to these cases should contact the Los Angeles Police Department at (877) LAPD-247.