Hadnot, a sophomore at Mandela High School, was shot at about 5:10 p.m. in the 5800 block of Bancroft Avenue.
Two other teens were killed last weekend in unrelated shootings, police said.
One of them, 17-year-old Christopher Jones, was shot as he helped his older sister put her 5-month-old daughter into a car in the 7400 block of Fresno Street at about 6:30 p.m. on Dec. 31, Oakland police Officer Jeff Thomason said.
His sister was also injured in the shooting but the baby was not hit by the gunfire, Thomason said.
Jones was a senior at East Oakland School of the Arts, part of Castlemont High School, assistant principal John Lynch said.
He was one of about 50 seniors at the school and was waiting to hear back from the four-year universities he'd applied to for the fall, Lynch said.
"Chris was definitely not in a gang," Lynch said.
Jones' senior classmates met with his parents shortly after he was killed to discuss his death, Lynch said.
The seniors then took it upon themselves to meet with the underclassmen to discuss Jones' murder and recent violence in their community, Lynch said.
"Our kids are really resilient," Lynch said. "They're dealing with it the best they can."
Jones' family and friends came together Sunday night for a candlelight vigil and a musical celebration of his life at Seventh Avenue Baptist Church, Lynch said.
Less than six hours after Jones was murdered, at about 12:10 a.m. on Jan. 1, 18-year-old Darnell Barr was fatally shot.
Barr, a Bay Point resident, was shot in the 3100 block of High Street, and was Oakland's first homicide victim of the new year, Thomason said.
Last Tuesday night, tensions between two groups led to a shooting at the intersection of 89th Avenue and D Street, Thomason said.
Six people were injured, including one bystander who was watching TV in his apartment when a bullet passed through the wall and hit him, Thomason said.
Two other men, Allen Collins, 22, and Donald Johnson, 46, were both found fatally shot in separate shootings in West Oakland on Tuesday and Wednesday, Thomason said.
The fatal shooting of Ishmael Knudson on Saturday marked Oakland's fifth homicide of 2011.
Knudson, 29, was found suffering from gunshot wounds around 7:30 p.m. in front of Campbell Market at 1539 Market St. and was pronounced dead at the scene, Joshi said.