Minneapolis homicide detectives were investigating an overnight shooting on a North Side block Monday that left a teenage girl dead — nearly two years after her brother was gunned down.

Friends in social media posts identified the victim as 17-year-old Serenity Shief. Her death was at least the city's 50th slaying of 2020.

Shief was shot in the head while sitting in a car in the Jordan neighborhood about 11:30 p.m. Monday, according to officials and emergency dispatch audio. She was driven to a hospital, where she died on the operating table, police said.

Police said nearby ShotSpotter sensors detected roughly 20 rounds of gunfire near the intersection of N. 24th and James avenues. But police didn't immediately find any spent shell casings or other evidence of a shooting, and officers worked late into the night to try to locate a crime scene. The car that brought the victim to the hospital was shot up, raising the possibility that she had been shot elsewhere.

Police said several witnesses were interviewed but there was no motive or suspect information.

The incident continued an exceptionally violent summer that has seen homicides and shootings surge, mirroring similar increases across the country since the killing of George Floyd and unrest that followed. Minneapolis has already eclipsed its homicide total from all of 2019, and the city could be headed for its most violent year in at least two decades. Shief was at least the seventh teen to be slain this year, MPD crime statistics show.

Her slaying was one of four shootings Monday that left six people shot, including a triple shooting earlier in the night in the 3400 block of S. 26th Avenue in which another 17-year-old girl was injured.

No arrests had been announced in any of the cases.

In the hours after Shief's death, social media lit up with posts from grieving friends and relatives about the young mother who went by "Ce Ce."

One post read: "[W]e tired of going to funerals ... we tired of having #LongLive in our bios. we tired of crying (bawling) our eyes out! We tired of hurting (for real)," one post read.

Anti-violence activist K.G. Wilson said he remembered Shief from one of the schools where he mentored kids.

"She was a very respectful young lady, and she was sweet to me, and she had just had a child," he recalled. "Just a young lady who was trying to finish school and became a young mother, and was moving on and tragically her life got taken, and here we are again."

He said he worried the constant drumbeat of death had left many people desensitized to the violence that is wracking neighborhoods.

"This is just the beginning of something, because whoever did this, first of all they're on the run, they're hiding and I'm quite sure that there's going to be some people angry about this who want revenge," Wilson said.

Shief's death left her family reeling anew. In September 2018 they buried her brother, Jamarius, 18, who was killed in a shootout at a North Side convenience store that left another man dead.

For weeks, Jamarius and Serenity's mother wrote in Facebook posts that she was bracing herself for the two year-anniversary of her son's death.

"September the 9th coming soon I'm not ready that makes two years my son been gone and never coming back (oh my God) I can feel it," one post read, dated Aug. 11. Two weeks later, her daughter was gone, too.